Since the industrial revolution, human activities have become a significant driver of Earth surface geological processes and ecosystem change. By the mid-20th century, the driver entered the "Great Acceleration" over the globe, when land-use and industrialization intensified soil erosion and metal pollution. However, the magnitude and timing of anthropogenic impacts vary widely across regions, sourcing from complex interactions between natural conditions and socio-ecological systems. This study presents a sedimentary record from Sihailongwan (SHLW) Maar Lake and integrates previously published data to examine human-environment interactions across China since the Great Acceleration. The results show that northeastern China experienced substantial deforestation and industrial expansion around 1950, 1975 and 2000 C.E., resulting in marked increases in soil erosion and heavy metal pollution in the region, as recorded by lithogenic element concentrations and ratios and anthropogenic metal fluxes in SHLW Lake. Compiled with other sedimentary records across China, there is a systemic intensification of anthropogenic processes represented by land use and industrialization since the Great Acceleration. However, these processes display clear differences in timing and composition, shaped by both social history and environmental conditions. In northeastern and inland China, resource-based economic development during 1950 and 2000 C.E. led to early industrialization, influenced by the regional rich natural resources and strategic location. In contrast, coastal regions, with an export-oriented economic model after 2000 C.E., experienced later industrial growth but had favorable geographical conditions for trade. Long-term monitoring and assessment at local and wider scales will aid in understanding these complex dynamics.

This analytical note demonstrates the suitability and risks of secondary reference materials (RMs)(e.g., SPEX-Li, GBW-Li) using multi-collector inductively coupled plasma mass spectrometry (MC-ICP-MS), proposes a validated strategy of using secondary RMs as isotope standard substances for isotopic analysis. The results indicate that secondary RMs show notable inter-batch variations, mainly attributable to differences in source materials, the delta 7Li differences of SPEX-Li and GBW-Li from different batches is up to 62.18%o and 68.65%o. Meanwhile, by using primary RM analyzed as a sample bracketed by secondary RM to derive a correction factor-delta 7Licorrected(%o), the values of GBW-Li-2 are consistent with conventional test values. Although the strategy does not aim to replace primary RMs, it offers a feasible alternative, especially in laboratories without primary RMs.

With the development of measurement techniques, K isotope composition (δ41K) has become a sensitive tracer of surface processes. The evolution of K-Li-B in salt lakes remains insufficiently constrained and a single isotope system cannot resolve the behavior of multiple elements. Bangor Co is a typical carbonate-type salt lake on the Qinghai-Tibet Plateau with relatively simple recharge condition and the absence of extensive K-salt mineral precipitation, making it an ideal site to study early-stage salt lake evolution. This study focuses on K isotope compositions in river (−0.12‰), cold springs (−0.72‰ to 0.02‰), and brines (−0.76‰ to − 0.36‰), together with hydrochemistry, Li and B isotopes. These data indicate that K in Bangor Co is mainly sourced from silicate weathering, geothermal inputs, and the redissolution of lacustrine sediments. The δ41K fractionation observed in the brines may reflect the important influence of clay mineral adsorption, with inferred K removal fractions of 0.29–0.55. Comparison of K, Li and B isotopes reveals decoupled geochemical behavior among elements and establishes a conceptual model for carbonate-type salt lakes. This study demonstrates that δ41K is an effective tracer in carbonate-type salt lake catchments. A multi-isotope approach provides a useful framework for understanding solute evolution in carbonate-type salt lakes and similar evaporitic systems.

Potassium isotopic compositions (b41 K) have emerged as sensitive tracers in modern environmental processes. Lakkor Co Salt Lake, situated within a critical tectonic zone of the Qinghai-Tibet Plateau (the Bangong-Nujiang tectonic belt), stands as a leading example of applying stable potassium isotopes to decipher diverse geochemical cycles in tectonically active regions. The results demonstrated that the potassium concentration in Lakkor Co can reach up to 2901 mg/L. A distinct potassium isotope fractionation is observed across the system. The b41 K values vary from -0.82%o to -0.05%o in recharge rivers, which are lower than the global riverine range reported in previous studies (-0.59%o to -0.08%o). In contrast, the surface brine of Lakkor Co exhibits b41 K values between -0.30%o and + 0.05%o, falling within the ranges of both modern seawater (-0.01%o to + 0.14%o) and chloride-dominated brines in the Qaidam Basin (-0.57%o to + 0.22%o). In combination with hydrochemical, b11B and b7Li data, the potassium in the Lakkor Co area is sourced from surface rock weathering and geothermal fluid. Moreover, weathering of ultra-high pressure metamorphic zones formed by deep subduction of oceanic crust may represent an additional source, which is supported by the anomalously low b41K values observed in the lake basin. This study investigates the sources, geochemical behavior and evolution process of potassium in the Lakkor Co Salt Lake; provide a theoretical basis for subsequent exploration and development of analogous salt lakes; and explore the elemental behavior of subducting oceanic crust. (c) 2026 China University of Geosciences (Beijing) and Peking University. Published by Elsevier B.V. on behalf of China University of Geosciences (Beijing). This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).

Holocene temperature variations exhibit significant spatial heterogeneity, yet their impacts on regional hydrological systems remain poorly understood. Here, we quantitatively reconstruct Holocene land surface temperature (LST) changes from the Jiangxigou loess record in the Qinghai Lake region using brGDGTs biomarkers and compare them with past meltwater variations on the Tibetan Plateau. Notably, while most global and regional records document the Holocene Thermal Maximum (HTM) between 9 and 5 ka, Jiangxigou exhibits progressive warming through the early-mid Holocene, reaching peak temperatures during the Mid-Late Holocene transition (5-3 ka) followed by gradual cooling. We attribute this anomalous thermal regime to combined solar activity and residual ice sheet effects. Crucially, the delayed HTM shows strong temporal coupling with amplified meltwater contributions, underscoring temperature's pivotal role in governing plateau meltwater dynamics. Our findings decode the hydrothermal coupling mechanisms of the "Asian Water Tower" during this climatic transition, offering vital benchmarks for projecting its water resource responses to future warming.

Potash, a strategic mineral resource that impacts the development of global agriculture and industry, has received considerable attention regarding its worldwide distribution, genesis, and exploration prospects. Influenced by various tectonic events and climatic changes throughout geological history, the distribution of potash resources exhibits significant spatio-temporal characteristics. Potash deposits have been documented in a variety of basin types globally, including stable cratonic basins, continental rift systems, foreland basins, intermontane depressions, and other tectonic settings. The metallogenic epochs range from the Cambrian of the Paleozoic to the Quaternary of the Cenozoic, with potash formation primarily occurring in the Paleozoic, followed by the Mesozoic, and the least quantity formed in the Cenozoic. Based on the unique metallogenic environments and occurrence characteristics of these mineral deposits, potash deposits can be classified into three main types: marine, continental, and marine-continental transitional facies. Among them, marine potash deposits are large in scale and mainly formed in stable cratonic basins. Continental potash deposits, on the other hand, are smaller in scale and mostly distributed in intermountain depression basins within continents, and primarily characterized by salt lake potash. Marine-continental transitional potash deposits exhibit both marine and continental features, are mostly distributed in continental rifts or marine-continental transitional zones, and have complex metallogenic processes. Previous studies indicate that potash deposit formation results from the interplay of multiple ore-controlling factors, including tectonics, paleoclimate conditions, material sources, paleogeographic environment, and marine geochemistry. The metallogenic regularity is primarily determined by the interaction of the three dynamic systems of “tectonics-climate--material source” in specific spatio-temporal context. As a result, potash deposits across different global regions and geological periods generally exhibit significant diversity in metallogenic patterns, reflecting their unique mineralization environments and evolutionary histories of tectonic processes. This heterogeneity in genetic mechanisms means that a single metallogenic model cannot universally explain the formation of all global potash deposits. Consequently, worldwide potash exploration faces substantial challenges. Moreover, the specificity of these mineralization mechanisms further exacerbates the highly uneven distribution of global potash resources, creating severe challenges for countries with urgent food security needs in achieving sustainable potash supply. Consequently, building upon existing resource development, it is necessary to systematically enhance potash exploration potential and ensure sustainable supply capacity through deep potash exploration, AI-powered predictions, rational utilization of unexploited potassium salt deposits and the search for undiscovered ones, as well as innovation in exploration technology systems. This requires systematic breakthroughs in metallogenic theory innovation, detection technology development, and comprehensive predictive models to advance potash resource exploration toward precision, intelligence, and sustainability–ultimately establishing a new global potash supply framework that balances resource security with ecological equilibrium.

Salt lake brine is a major source of global lithium and hold a strategic importance for the energy transition.The Four-Lake area of the Qaidam Basin(Qarhan,East Taijinaier,West Taijinaier,and Yili-ping)is the most significant brine-type lithium enrichment area in China.Elucidating its resource enrich-ment and mineralization mechanisms are critical for safeguarding supply security.Previous work has empha-sized metallogenic regularity and materials sources.But a systematic summary of lithium behavior and loss mechanisms along the source-transport-sink process remains incomplete,introducing uncertainty into re-source assessments.Focusing on the Four-Lake area,this study uses elemental ratios and lithium isotopes to investigate multipath loss mechanisms operating during transport and enrichment:(1)clay adsorption:clay minerals progressively remove dissolved Li through surface adsorption,ion exchange,and lattice fixa-tion,producing marked increases in δ⁷Li in the residual fluid;(2)reverse weathering:authigenic clay for-mation within the lacustrine system incorporates or adsorbs Li;(3)salt minerals precipitation:during evaporite crystallization,Li is sequestered via lattice incorporation and fluid inclusions;(4)freshwater mixing and dilution:freshwater and brine mixing zones dilute Li from lake centers toward margins,a pro-cess intensified under global warming as precipitation and runoff increase;and(5)biotic processes:micro-bial adsorption and microbially induced mineral precipitation contribute secondary Li losses.These results provide a new perspective for improving resource evaluation and refining exploration strategies.

Lithium is a strategically important critical metal primarily hosted in brines and hard-rock deposits. Growing demand has prompted increasing attention to lithium in lacustrine clay sediments as a potential complementary host. The Qaidam Basin supplies similar to 80% of China' s lithium from brines, yet faces increasing supply pressure. Anomalous lithium enrichment has been reported in coeval lacustrine clays of the secondary Mahai Basin. This study investigates phase-specific lithium distribution and isotopic signatures (delta Li-7) in Mahai Basin lacustrine clays using XRD and Tessier sequential extraction, combined with major/trace element and lithium isotope analyses of different phases. XRD results show that silicon-bearing minerals comprise similar to 61% and clay minerals similar to 26-27% of the bulk mineralogy. Lithium is overwhelmingly hosted in the silicate phase (89.5%). delta Li-7 values vary markedly among phases: water-soluble (-18.79 to + 26.99 parts per thousand), ion-exchangeable (-16.44 to + 19.12 parts per thousand), and silicate (+0.28 to + 3.65 parts per thousand). The clays formed under cold, arid conditions dominated by physical weathering of felsic igneous rocks. Elevated water-soluble Li relative to ion-exchangeable Li is attributed to competitive adsorption inhibition. The water-soluble delta Li-7 signature is consistent with regional brines, and calculated fractionation factors (0.973-0.995) align with lithium adsorption onto montmorillonite. Silicate delta Li-7 values fall within the range of upper continental crust, indicating dominant continental weathering input. Integration with Sr and B isotopes reveals multi-source lithium contributions from silicate weathering of surrounding orogens, fluvial input (Yuka River), and deep Ca-Cl fluids. These findings clarify lithium sources, phase partitioning, and the role of competitive adsorption in lithium mobility, providing a scientific basis for understanding lithium enrichment processes in lacustrine clay sediments of salt-lake systems.

The Western Kunlun region of the Qinghai-Xizang Plateau is a premier lithium province characterized by the coexistence of super-large pegmatite and brine-type lithium deposits. This spatial association provides a unique laboratory to investigate the lithium cycle from the lithosphere to the hydrosphere. This study utilizes hydrochemistry and a multi-isotope (δ7Li、δ11B、87Sr/86Sr) framework across 50 water samples from the Tianshuihai-Kushui Lake basin to quantify lithium sources and enrichment mechanisms. Results identify three End-members with distinct geochemical fingerprints. The water-rock interaction during the upwelling of deep fluids is the key process for lithium enrichment in Kushui Lake. Sr isotope mass balance and aqueous geochemical calculations indicate that this process contributes 88.6% of Sr and 64.7% of Li to the system. Supergene lithium enrichment follows a three-stage evolution: evaporation-driven linear accumulation, an adsorption-buffering phase, and terminal-basin selective enrichment. Based on these findings, this study establishes a ”mobilization-migration-enrichment” lithium cycle model. This model represents a transition from ”endogenous enrichment” in the lithosphere to ”exogenous ore formation” in the hydrosphere, this coupled genetic model is likely a common phenomenon in Li-rich salt lakes across the Kunlun orogenic belt on the Qinghai-Xizang Plateau. These insights offer a novel perspective for mineral exploration and enhance our understanding of lithium metallogeny in analogous geological settings worldwide.

Abstract As a highly volatile heavy metal, Hg is transported over long distances in the atmosphere and enters global ecosystems via Hg(II) wet deposition and Hg(0) dry deposition. The Chinese Loess Plateau develops loess‐paleosol sequences (eolian deposits) reflecting glacial‐interglacial cycles. Here, we investigate the Hg concentration and isotopic composition of loess‐paleosol sequences covering three glacial‐interglacial cycles (spanning 350–80 ka). Paleosol layers display higher THg, Δ199Hg, and Δ200Hg values than loess layers, meaning enhanced Hg(II) wet deposition during interglacials. Based on a Δ200Hg‐based mixing model, Hg(II) wet and Hg(0) dry depositions account for 42% and 58% of Hg input into the Chinese Loess Plateau during interglacials but 21% and 79% during glacials, respectively. This work highlights a strong climatic control on atmospheric Hg deposition at glacial‐interglacial time scales, and suggests that atmospheric Hg deposition will likely increase in middle latitudes without considering perturbations of anthropogenic emissions.

The source-to-sink system of a watershed is linked to tectonics, lithology, and climate, and includes erosion, sediment transport, and geomorphic change. Geological reconstructions of such systems are poorly understood, especially in arid and semi-arid regions with sparse geological evidence. Here, we reconstruct a watershed history from the Tarim River Basin since the Last Glacial Maximum (LGM) using river water geochemistry (including alkalinity and total dissolved solids) and sediment records from Lop Nur Salt Lake. Modern river geochemistry reveals that water availability and material supply control chemical weathering patterns, with significant spatiotemporal variations in sediment transport dynamics between hydrological seasons. Carbon proxies (total carbon, labile organic carbon, and related indicators) of borehole sediments suggest a wet environment in the Lop Nur area during the Holocene Megathermal, with a relatively high sediment carbon content. During the LGM, the climate was dry with lower sediment carbon. Geomorphological evidence can be used to further constrain sediment transport histories. We interpret millennial-scale paleorecords in the light of modern seasonal dynamics to reconstruct the evolution of the regional source-to-sink system. This analysis points to astronomical forcing as a key regulator of the relative contributions of sediment sources.

High silica granites may host major rare metal deposits. The petrogenesis of these granites, some of which have very low Zr/Hf, Nb/Ta, and Eu/Eu* ratios, has been highly debated. The existing views mainly favor either extreme magmatic fractionation or fluid‐magma interaction. Contrary to these interpretations, we demonstrate that the distinct chemistry of high‐SiO 2 granites can be inherited from partial melting of their sedimentary source rocks. The wide range in Ɛ Hf ( t ) values (−14 to −1.3), Nd‐Hf isotope decoupling,and correlations of Hf‐B isotopes with major and trace element abundances and ratios are best understood as melting‐induced mixing of diverse source lithologies with contrasting abundances of zircon (a low Lu/Hf phase) and high Lu/Hf phases. This process also leads to positive correlations of Ɛ Hf ( t ) with muscovite modes and negative correlations of δ 11 B with muscovite modes. Based on the above findings, there are several practical implications: (a) the extremely low Zr/Hf, Nb/Ta and negative Eu/Eu* anomalies could be inherited from protoliths; (b) the Lenglongling leucogranites represent “pure” S‐type granites with relatively high Ɛ Hf ( t ); and (c) using Hf isotope alone may lead to incorrect interpretation of mantle contribution.

Coal fly ashes (CFAs) are an alternative resource of rare earth elements and yttrium (REY). China is the largest producer of CFAs in the world and is likely to hold substantial reserves of CFA-REY resources, while nationwide research on REY resource in Chinese CFAs is lacking. In this work, CFA samples were collected from 118 coal fired power plants (CFPPs), including eight subjected to long-term monitoring. Based on this, a machine-learned (ML) REY concentration predictive model was developed with a deviation of 16 %, which showed REY concentration and the proportion of air-dried-basis ash yield in coal, and CFPP boiler type were the three governing factors regulating REY concentrations in CFAs. Using this ML model and a unit-based database of Chinese CFPPs, REY concentrations in CFAs from 1062 additional CFPPs were predicted, who accounted for 89.2 % of national coal consumption. Promising CFA-REY resources were defined as those containing >= 300 mg/kg REY in CFA, and were concentrated in North (Inner Mongolia, Shanxi, and Hebei Provinces), East (Shandong, Jiangsu, Zhejiang, and Anhui Provinces), South (Guangdong Province) and Southwest (Guizhou Province) China. Moreover, using a unit-based estimation model, the total amount of rare earth oxides from unutilized CFAs with REY recovery potential in China is estimated to be about 74,300 tons/y, which would meet six months of global demand and have a gross value of US $ 4.2 billion.

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 δ7Li values, varying from 4.89‰ to 16.02‰. Notably, the lowest and highest values are observed in cold springs. Additionally, the concentrations and δ7Li 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 δ7Li 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.

Riverine boron (B) and its isotopic compositions (δ11B) are commonly used to trace silicate weathering within watersheds, but its sources and isotopic fractionation mechanisms remain contentious. In this study, we collected the seasonal river waters of the Buha River, the largest inlet river of Qinghai Lake, which is sensitive to climate change, and analyzed its seasonal variations of the major ions, B concentrations, and δ11B, to explore its sources and controlling factors. The results indicate that B in the Buha River predominantly originates from weathering of silicate rocks, with significantly seasonal variations in the geochemical behaviour of B isotopes. In the rainy seasons, the riverine B isotopic fractionation is primarily controlled by weathering of silicate rocks under the influence of hydrological conditions, where clay minerals preferentially absorb 10B, leading to the enrichment of heavier B isotopes in river waters. In contrast, in the dry seasons, the B of river waters may mainly come from the recharge of groundwater (whose δ11B with a notable pH dependence); owing to prolonged retention of fluids, the steady state of δ11B is reached by the isotopic equilibrium through adsorption of clay minerals. This study highlights that the seasonal variations in riverine δ11B in semi-arid regions are jointly governed by silicate weathering, hydrological conditions, and water-rock interactions, with water pH and rainfall as key regulators. Consequently, riverine δ11B in the rainy seasons under semi-arid climatic conditions can effectively trace hydrologically-controlled silicate weathering processes within the watershed.

The genesis and evolutionary pathways of potassium resources in salt lakes form the scientific foundation for sustainable exploration and utilization of these critical mineral reserves. Potassium isotope system (delta K-41), characterized by significant mass-dependent fractionation, has emerged as an effective tracer for investigating geological processes and material sources. This study presents a comprehensive geochemical investigation of brine salts, intercrystalline brines, and river waters collected from the Qaidam Basin on the northern Tibetan Plateau, China. The ion compositions, hydrochemical characteristics, and potassium isotopic compositions of the samples were analyzed. Analytical results reveal substantial spatial heterogeneity in potassium concentrations ([K+]) across different sample types, ranging from less than 0.01 x 10(3) mg L-1 to similar to 21.12 x 10(3) mg L-1. A distinct [K+] hierarchy emerges: river samples < freshwater lakes < semi saline lakes < brine lakes < intercrystalline brines. Concurrent delta K-41 values exhibit significant variability (-0.77 parts per thousand to + 1.31 parts per thousand), demonstrating systematic correlations with both [K+] concentrations and basin-scale structural features, as evidenced by comparative analysis with published delta Li-7 and delta B-11 datasets. Multivariate isotopic analysis (delta K-41-delta Li-7-delta B-11) coupled with hydrochemical fingerprinting reveals a polygenetic potassium origin for Qaidam's brine systems, involving: multiple mixture of rivers, deep groundwater via fractures (oil field brines, hot springs, etc.), and low-temperature weathering processes of K-rich rock. Notably, delta K-41 signatures show systematic differentiation between two major brine types. The delta K-41 values of chloride type salt lakes is relatively small (-0.57 parts per thousand to 0.22 parts per thousand), whereas those in sulfate type salt lakes is much larger (-0.77 parts per thousand to 1.31 parts per thousand). The results suggest that delta K-41 is a powerful tracer not only for indicating changes in sources but also for reflecting the evolutionary processes of brine.

The water-rock interaction has a significant impact on reconstructing climatic and environmental changes using loess deposits. Lithium isotopes (delta Li-7) are important tracers to track this process. This study examined the Li contents and delta Li-7 values of different phases (water, weak acid leachate and residue were recorded as [Li](water), [Li](leachate), [Li](residue), delta Li-7(water), delta Li-7(leachate) and delta Li-7(residue)) within the upper 22 m Weinan loess-paleosol sediment located on the southeastern margin of the Chinese Loess Plateau. Significant variations were observed in both the [Li] and delta Li-7 values of different fractions within the loess. The water fraction samples have the lowest [Li](water) with less than 0.05 mu g/g. The leachate samples show relatively low [Li](leachate) levels ranging from 0.67 mu g/g to 2.45 mu g/g. In comparison, the residue samples exhibit higher [Li] values than the leachate samples, with the concentrations varying from approximately 29.45 mu g/g to 41.28 mu g/g. The delta Li-7(water) values are all higher than those of the corresponding leachate and residue, ranging from 14.7 parts per thousand to 28.2 parts per thousand. Additionally, the delta Li-7(water) values vary from -8.4 parts per thousand to 8.7 parts per thousand. The delta Li-7 of residue samples are relatively stable, ranging from -0.6 parts per thousand to 1.7 parts per thousand, with an average delta Li-7(residue) = 0.5 +/- 1.3 parts per thousand. The results indicate that the [Li](leachate) in Weinan Loess-paleosol sediments has excellent potential to indicate the variations of East East Asian summer monsoons during the last glacial-interglacial cycle, compared to the values of grain size, magnetic susceptibility, and CaCO3 content. Meanwhile, the delta Li-7(leachate) of loess not only can be utilized for tracing the pedogenic processes of weathering, eluviation, and migration, as well as for tracing groundwater impact. In the upper 15 m, the delta Li-7(leachate) can be employed to track soil water migration processes and the magnitude of pedogenic processes in loess at various time periods. Below the calcium carbonate accumulation layer (CAA, >15 m), there is groundwater, and CAA has impeded the flow of groundwater, making it difficult for the influence of groundwater to penetrate the CAA layer. Due to the prolonged exposure to capillary water, the acid-soluble phase lithium represents the lithium adsorbed by loess continuously absorbed from groundwater. delta Li-7(leachate) and delta Li-7(water) had basically reached equilibrium, with values of alpha ranging from 0.98 to 0.99 and an average value of alpha at 0.98. Our work thus shows that the delta Li-7(leachate) of loess-paleosol sediments may reflect equilibrium fractionation between sediments and groundwater, rather than pedogenic processes at the layer near groundwater.