Resolving suspended sediment (SS) provenance is critical for managing land degradation and contaminant transport, yet it remains challenging due to the complex coexisting surface and subsurface pathways in karst systems. This study quantified the scale-dependent dynamics of sediment sources and transport pathways in a karst agroforestry catchment (Houzhai, SW China). Using a composite fingerprinting approach (geochemistry, 137Cs, magnetic susceptibility) within a nested monitoring network, we compared SS provenance between a headwater (1.26 km2) and the full catchment (73.39 km2). Results revealed a fundamental, scale-dependent reorganization of sediment delivery. At the headwater scale, sediment export (D50 =17 mu m) was dominated by surface runoff carrying contemporary agricultural soils. At the catchment scale, the integrated epigenic conduit network became the primary pathway, exporting finer sediments (D50 = 7 mu m) overwhelmingly sourced from legacy fissure soils and clastic rock pieces. This source shift was corroborated by hillslope erosion monitoring confirming local-scale agricultural dominance, sediment yield calculations demonstrating that subsurface flux dominates at the catchment scale, and storm hysteresis analysis revealing contrasting transport dynamics consistent with pathway-specific sediment delivery. Our findings demonstrate that subsurface connectivity and lithology supersede land-use effects in controlling sediment export. Effective karst management must therefore shift from a land-use-centric approach to one prioritizing stabilization of lithogenic sources (e.g., clastic rock outcrops) and sediment interception along major subsurface conduits.

Accurate mapping of cone karst hills, a typical landform in tropical-subtropical karst landscapes, is essential for understanding karst geomorphology and supporting environmental management. However, the complex topography of these areas poses significant challenges for conventional mapping approaches. This study presents an advanced deep learning approach for cone karst hill identification in China's Guizhou Karst Plateau, integrating multi-source data, including high-resolution Digital Elevation Models (DEM), DEM-derived data and spectral information with U-Net and DeepLab V3+ architecture. The results demonstrate that the U-Net model consistently outperformed DeepLab V3+, achieving higher accuracy and adaptability across all data configurations for cone karst hills recognition. The optimal configuration (DEM, slope and local relief) showed notably superior performance compared to other tested configurations. Rigorous validation in the Xinyi and Anlong regions of southwestern Guizhou confirmed the method's reliability and transferability. This research establishes a scalable and transferable processing workflow that enables high-precision, large-scale mapping of individual cone karst hills, with direct applications in geomorphological research, sustainable land management, and conservation planning for fragile karst ecosystems.

It is essential to distinguish the effects of climate signals and cave microenvironments on speleothem 518O, 513C, and element/Ca records, because cave microenvironments can interfere with the reconstruction of climate signals preserved by speleothems. However, it remains difficult to separate the impacts of direct climate signals and cave microenvironments-including cave air temperature and CO2 concentration-on these proxies, even after numerous cave monitoring and laboratory simulation experiments. In this study, we compared outdoor Artificial Cave monitoring with natural cave monitoring, providing an innovative and efficient method to discriminate the effects of climate signals and cave microenvironments on the proxies. We presented seven years of time-series data from Shawan Cave (natural cave) and more than two years of time-series data from the outdoor Artificial Cave located in Guizhou Province, Southwest China, for 518O, 513C, and elemental compositions of cave drip water along with microenvironmental conditions. In Shawan Cave, the seasonal changes in drip water 518O and 513CDIC, which showed a significant inverse correlation with cave airpCO2, were attributed to the wide range of cave air pCO2 (972-21,627 ppm), The irregular seasonal changes in drip water Mg/Ca were affected by the opposing seasonal variations in rainfall amount and cave airpCO2. In contrast, in the Artificial Cave, the wider range of cave air temperature (11.78-25.25 degrees C) appeared to influence the seasonality of cave water 518O and Mg/Ca values. Meanwhile, the 518O and Mg/Ca values of water isolated from the cave were mainly affected by rainfall 518O and rainfall amount, respectively. The 513CDIC values in cave water and in water isolated from the cave were primarily influenced by rainfall amount, because the narrow range of cave airpCO2 was insufficient to drive a notable change in cave water 513CDIC. Our study highlights that cave microenvironments, rather than direct climate signals, are key drivers of seasonal amplitudes in speleothems proxies in caves with wide ranges of cave air temperature and pCO2. When the ranges of cave air temperature and pCO2 are narrow, speleothem proxies primarily record precipitation and air temperature.

Persistent hydroclimatic extremes strongly affect water resources and ecosystems in Northeast Asia, but instrumental climate and runoff records are too short to characterize multidecadal wet–dry variability. We developed two tree-ring-based seasonal precipitation reconstructions for western and eastern Northeast China and compared them with a moisture-sensitive precipitation record from the Russian Far East. The western reconstruction spans 1829–2022 and targets previous September–current June precipitation, whereas the eastern reconstruction spans 1680–2022 and targets January–July precipitation. Both reconstructions show significant precipitation signals and acceptable verification skill. Comparisons with natural runoff and discharge records indicate that reconstructed precipitation variability is expressed in regional runoff, particularly at low-frequency to decadal timescales.The reconstructions reveal both coherent and regionally divergent hydroclimatic regimes. A common wet interval occurred during 1855–1867, whereas a pronounced common dry interval occurred during 1911–1928, including the well-known 1920s drought. Cross-regional comparison shows that drought extremes were more spatially coherent than pluvial extremes, and duration–severity analysis identifies persistent regimes with large cumulative anomalies. Composite diagnostics associate coherent wet extremes with El Niño-like tropical Pacific warming, positive 500-hPa geopotential height anomalies, and enhanced 850-hPa moisture flux convergence. Coherent droughts were associated with La Niña-like cooling and weaker or displaced moisture convergence. These results show that tree-ring precipitation reconstructions can provide a long-term perspective on runoff-relevant hydroclimatic persistence and moisture-transport variability across Northeast Asia.

Karst cave systems represent significant reservoirs of Radon-222 (222Rn), which is a natural radioactive and class-I carcinogenic pollutant whose risk is amplified by increasing cave tourism. However, the dominant sources, driving mechanisms, and resulting exposure levels in these subterranean environments remain poorly understood. Therefore, we conducted a comprehensive monitoring campaign across 24 karst caves in Southwest China while integrating field measurements with controlled simulations and dose assessment. Results indicate that both the carbonate bedrock and overlying soil layer act as primary sources of cave 222Rn, with soil contributing substantially more due to secondary radionuclide enrichment during weathering. Seasonal ventilation, driven by temperature-induced airflow (chimney effect), was identified as the dominant factor controlling 222Rn variability, resulting in three distinct seasonal patterns: summer-high/winter-low, winter-high/summer-low, and annual-average. Further, we further elucidated the source-transport-sink dynamics governing 222Rn behavior in cave systems and highlighted the critical role of cave structure in modulating airflow and 222Rn accumulation. Although the short-term exposure risk for tourists is negligible, the annual effective radiation dose experienced by occupational groups in nine tourist caves exceeds regulatory limits, underscoring the necessity of the development of targeted protective measures. This study elucidates the source-transport-exposure pathway of 222Rn pollution in karst cave environments and provides a scientific basis for stratified risk management. Our findings emphasize the importance of integrating environmental process research into public health protection frameworks for high-risk micro-environments.

Cave drip water is a fundamental carrier of climatic and environmental information, and its geochemical signatures are widely employed in speleothem-based paleoclimate reconstructions. While are well established, the role of rainfall intensity and vegetation-driven infiltration dynamics in shaping these signals remains insufficiently constrained. To address this, we carried out seven years of monitoring in Shawan Cave, a shallow karst cave system in Southwest China, integrating rainfall observations, continuous drip rate measurements at 30-minute resolution, and stable isotopes and elements/Ca data from drip water. Our results showed that drip water was present in both the dry and wet seasons from 2017 to 2019, whereas it was intermittently interrupted from 2020 to 2023 drip water, with more observed during the wet season and less during the dry season. This may be attributed to the deeper root systems of vegetation, which alter soil moisture and the amount of rainfall required to penetrate the soil and generate infiltration into the karst cave system, thereby changing the water reservoirs feed drip water over time. We propose that vegetation recovery, by influencing evaporation, can modulate drip water flow paths and thereby drive the enrichment of drip water 518O. Intriguingly, although drip water 518O during 2017-2018 did not fully reflect changes in rainfall 518O, during 2022-2023 it appeared to inherit the 518O signal of heavy rainfall. This indicates that drip water 518O has gradually evolved from reflecting annual or multiyear rainfall amounts to primarily recording the heavy rainfall of the summer monsoon. These observations demonstrate that drip water signals are not simply a direct record of rainfall but are mediated by subsurface hydrological processes. We propose that the combined effects of reservoir-feeding drip water and flow path change over time are critical in governing the transmission of rainfall signals into cave environments. Recognizing the influence of vegetation change and reservoir evolution refines the interpretation of speleothem proxies, enabling more reliable reconstructions of monsoon variability at sub-annual to interannual timescales.

Ridge tillage is a major farmland management practice in arid and semi-arid areas; however, knowledge regarding wind velocity fluctuations and sediment transport characteristics over the ridged surface remains limited. This study used wind tunnel experiments to reveal the mechanism by which changes in ridge size and configuration affect wind velocity fluctuation near the surface and further influence the sediment transport rate (q). Results showed that ridge covering, compared with no ridges, significantly reduced the intensity and variation amplitude of instantaneous wind velocity (ui) in the lower layer, and changed its structure with measurement height (h). Wind velocity fluctuation intensity (uv) over all the ridges increased with incoming friction velocity (u*r), but first increases and then decreases with h. At the surface (h=0.01 m), the average wind velocity fluctuation intensity (uv_ave) increased linearly with both ridge spacing (L) and u*r, whereas its relationship with ridge height (H) was not obvious. The spatial variation in uv led to an uneven wind erosion distribution on the bed surface. With different ridge sizes, location and extent of wind erosion and deposition areas were significantly different. Finally, a quantitative relationship between the uv_ave and q under ridge-shaped microtopography conditions was established.

The carbon budget of maize croplands has been widely studied across the Chinese Maize Belt. However, the effects of drought on ecosystem-scale carbon fluxes in rain-fed maize croplands remain poorly understood in Southwest China. To address this gap, we conducted long-term, continuous eddy covariance measurements of carbon fluxes at a rain-fed maize field in Guizhou Province from 2022 to 2025. During the maize growing season, the mean net ecosystem exchange (NEE) was −310 ± 21 g C m−2, with over 50% of the total seasonal NEE occurring in July. Interannual variability in the NEE was primarily driven by prolonged dry spells during the reproductive stage. Maize cropland without straw return acted as a net C source when harvest removals were considered. We therefore recommend promoting straw return practices in the region to strengthen soil carbon sequestration capacity and enhance agroecosystem resilience to drought. And further research is needed to evaluate the role of straw return practices on the carbon budget in the area.

The Taklimakan Desert Highway shelterbelt is the world’s largest ecological protection system established along a highway in a shifting desert environment and plays a critical role in mitigating wind-blown sand hazards and ensuring transportation safety. However, its long-term stability and protective capacity after more than two decades of operation remain insufficiently understood. In this study, Landsat imagery from 2005 to 2025 was used to monitor the long-term evolution of the shelterbelt along the Middle Section (~180 km) of the Taklimakan Desert Highway. A Random Forest classifier was employed to extract shelterbelt distribution, and classification results were validated using high-resolution Google Earth imagery and unmanned aerial vehicle observations. To quantify shelterbelt condition, a Shelterbelt Stability Index (SSI) was developed by integrating fractional vegetation cover (FVC), connectivity index (CI), percentage of landscape (PLAND), and perimeter-area fractal dimension (FRAC). The shelterbelt experienced initial seedling decline from 2005 to 2011, followed by progressive restoration during 2011–2020 and finally entered a stable saturated stage after 2020. Affected by saline water drip irrigation, wind-sand erosion and pipeline clogging, the overall vegetation condition deteriorated continuously before 2011. After targeted irrigation regulation, optimization of planting patterns and replanting measures were implemented; the degradation trend was reversed, contributing to the sustained improvement of vegetation thereafter. Significant spatial heterogeneity was observed along the highway, with certain sections maintaining high continuity and vegetation coverage, while others exhibited fragmentation, local discontinuities, area shrinkage, and increasing structural complexity. The proposed SSI effectively captured long-term structural dynamics and identified vulnerable sections subject to degradation. This study provides new insights into the life-cycle evolution of desert highway shelterbelts and offers scientific support for the sustainable management of ecological protection systems in arid environments.

The Chudong PbZn deposit, located in the southern segment of the Ailao Mountain metallogenic belt, is controlled by the coupled effects of fault structures, mafic intrusions, and organic-rich sedimentary strata. The ore body is hosted within a fault-fracture zone developed in the siltstone layers of the Xiamidi Formation of the Carboniferous System. It is spatially associated with a NW-trending F3 fault and basic intrusive rocks. The deposit exhibits an average combined Pb + Zn grade of 5.89%. Rock geochemical analysis indicates that the basic rocks are of island arc tholeiitic basalt origin, reflecting a post-arc extension setting. The mineralization of the Chudong lead–zinc deposit occurred in two main stages, with carbonate–siliceous hydrothermal activity followed by the main sulfide precipitation. Based on geological and geochemical evidence suggests that deep magmatic-hydrothermal fluids mixed with basin brines to generate the primary ore-forming fluids. Organic-rich strata (average TOC = 2.72%) may have provided reduced sulfur that promoted PbZn sulfide precipitation within the fault-fractured zones. This genetic model indicates a close relationship between mineralization, fault-controlled fluid migration, mafic magmatism, and hydrocarbon-bearing sedimentary sequences. Wide-area electromagnetic and dual-frequency induced polarization surveys reveal strong correlations between geophysical anomalies and known ore bodies and delineate several prospective exploration targets. Combined with the regional characteristics of polymetallic mineralization in the Ailao Mountain belt, a structural–intrusive coupling metallogenic model is proposed. In this model, primary faults and intrusions control ore-fluid migration, secondary faults localize mineralization, and fault intersections favor ore accumulation. This model provides an important framework for deep and concealed ore exploration in the Ailao Mountain metallogenic belt.

Lignocellulosic hydrolysate is rich in various fermentable sugars, such as glucose, xylose, and cellobiose. Utilizing these sugars for L-lactic acid fermentation represents a promising strategy for the high-value utilization of biomass. However, when mixed sugars serve as carbon sources, microorganisms typically undergo carbon catabolite repression (CCR) at the initial fermentation stage, which significantly compromises both the yield and productivity of L-lactic acid. To clarify CCR mechanisms and explore effective mitigation strategies, Bacillus coagulans DSM 2314 was used as the fermentative strain, the effects of pH and temperature on fermentation with single and mixed carbon sources were examined, and L-lactic acid yields, productivities, and key enzymatic activities across different fermentation systems were systematically compared. The results showed that in glucose-containing mixed-sugar systems, glucose imposed strong CCR effects on both cellobiose and xylose. Under optimal conditions (initial total sugar concentration of 50 g/L, pH 7.0, and 45 °C), L-lactic acid yields increased in the following order: glucose/xylose (15.58 g/L) < glucose/cellobiose (29.65 g/L) < glucose (31.87 g/L). In contrast, in the glucose-free cellobiose/xylose system, both sugars were nearly co-consumed by B. coagulans DSM 2314, and L-lactic acid production was not significantly diminished by the mixing of carbon sources (xylose (27.45 g/L) < cellobiose/xylose (28.64 g/L) < cellobiose (29.60 g/L)). Under replicated optimal condition experiments, analyses of sugar consumption rates and enzyme activities further confirmed that the CCR between cellobiose and xylose was significantly weaker than in other mixed-sugar systems, with the L-lactic acid yield in the cellobiose/xylose system 1.61-fold higher than in the glucose/xylose system. These findings demonstrate that substituting glucose with cellobiose in mixed-sugar fermentation is an effective approach to mitigating CCR, providing a theoretical basis for efficient L-lactic acid production from lignocellulosic hydrolysates.

Southwest China's karst region has rapidly dissolving carbonate rock,shallow soils,and connected surface-subsurface drainage.Water,soil,and element cycles therefore respond quickly to climate and land-use change.For the Institute of Geochemistry's 60th anniversary,we review its karst biogeochemical and ecological research through Watershed Earth System Science(WESS)and Earth Critical Zone science.The synthesis uses long-term observations,flux measurements,isotope tracing,remote sensing,and socioeconomic surveys.Results show that the dual structure controls water pathways and whether soil is eroded at the surface or lost underground.Carbon,nitrogen,and sulfur are repeatedly retained and transformed at canopy,moss,soil,and bedrock interfaces,creating rapid responses to acid deposition,fertilization,and climate anomalies.Carbonate Weathering coupled with Aquatic Photosynthesis(CCW)links weathering-derived inorganic carbon to biological uptake and organic-carbon preservation.Ecological projects,urbanization,and migration jointly affect rocky-desertification recovery and regional carbon storage.The studies connect interface reactions with watershed transport and Socio-Ecological System(SES)governance.They inform zoned restoration,regional carbon accounting,and sustainable rural development.

Understanding the spatial distribution of tree growth sensitivity in response to climate change is essential for developing effective adaptive forest management strategies, particularly in vulnerable ecotones and transitional zones. Here, we present a network of 70 tree ring width chronologies from 12 tree species to systematically investigate the radial growth responses to key climatic factors, including temperature, precipitation, and drought (scPDSI), across the North-South transitional zone in China (NSTZ). Our analysis indicates that precipitation in the previous September (r = 0.005 - 0.503), January of the current year (r = 0.001 - 0.297), and late spring to early summer (April to June, r = 0.003 - 0.535) exerts a positive influence on the growth of most trees (chronologies > 50), whereas temperature suppresses tree growth in May (r = -0.443 - -0.004) and December (r = -0.396 - -0.026) of the current year. Further redundancy (RDA) and GeoDetector (GD) analysis indicates that the spatial variability of growth sensitivity is primarily governed by combined geographic, aridity gradients, and species, with local microclimatic variables such as vapor pressure deficit (VPD) and soil moisture exerting comparatively weaker influences. Multi-model projections under the SSP2-4.5 and SSP5-8.5 scenarios suggest that the transitional zone is likely to experience a drier and increasingly heterogeneous eco-climatic regime (the mean coefficient of variation > 0.25). Such changes may intensify the spatial divergence and potential destabilization of tree growth-climate relationships, posing challenges for forest ecosystem long-term sustainability.

Although anthropogenic greenhouse gas emissions are widely regarded as the major cause of ongoing global climate change, isolating anthropogenic impacts on climate is difficult due to the internal variability of the climate system and the brevity of the observational record. Here we attempt to discern a human signal in recent climate change using a 400-year reconstruction of the self-calibrating Palmer Drought Severity Index for the southeastern Tibetan Plateau, where current warming is more pronounced than most other places. Our results highlight a trend towards progressively drier conditions, while the most recent drought and wetness events are ranked as the second most severe throughout the entire reconstruction. We conclude that anthropogenic influence on climate in this region, which is clearly detected at the end of the 20th century, will become stronger in the foreseeable future.

Karst cave systems represent significant reservoirs of ²²²Rn, a natural radioactive and class-I carcinogenic pollutant whose risk is amplified by increasing cave tourism. However, a systematic understanding of its dominant sources, governing environmental processes, and resulting exposure levels remains limited. To address these gaps, we conducted a comprehensive monitoring campaign across 24 karst caves in Southwest China, integrating field measurements with controlled simulations and dose assessment. Results indicate that not only the carbonate bedrock but also the overlying soil layer serves as the primary source of cave ²²²Rn. Seasonal ventilation driven by temperature-gradient-induced airflow is the main control on cave ²²²Rn variability, leading to three distinct concentration patterns: summer-high/winter-low, annual-average, and winter-high/summer-low. We further deciphers the source-transport-sink processes governing ²²²Rn behavior in cave systems, providing deterministic controls on its accumulation patterns and migration pathways. Although tourist exposure is negligible, occupational workers require tailored protective measures. This study elucidates the source–transport–exposure pathway of ²²²Rn pollution in subterranean environments and provides a scientific basis for stratified risk management, highlighting the necessity of integrating environmental process understanding into public health protection strategies for specific micro-environments.

Efficient nitrogen removal after organic capture is challenging through conventional nitrification-denitrification process. Two biofilm-based anoxic/oxic reactors, with a single intermittent zone (R1) or dual intermittent zones (R2), were compared in treating carbon-limited wastewater. Intermittent aeration integrated partial nitrification-anammox (PNA), partial denitrification-anammox (PDA), and denitrification, with anammox-related pathways contributing over 75% nitrogen removal in both reactors. As nitrogen loading rate increased from 0.14 to 0.19 kg-N m-3 day-1, nitrogen removal efficiency in R1 dropped from 74.3% to 46.0%, while R2 maintained 76.6% removal at low HRT of 6 h. The dual intermittent aeration strategy improved nitrogen removal capacity by enhancing PNA in the first intermittent zone and reducing effluent fluctuation in the second. Anammox bacteria (Candidatus Brocadia, relative abundance: 0.95-2.48%) were enriched across all zones, supporting efficient PNA and PDA. These findings suggested that dual intermittent aeration enhanced anammox in pre-anoxic processes for carbon limited wastewater treatment.

Due to the implementation of various vegetation restoration measures, vegetation recovery is remarkable in karst areas of Southwest China, which is the main region for global greening. However, the effects of natural vegetation restoration on the soil profile microenvironment, particularly in karst regions, remain largely unknown. From 2018 to 2021, we continuously monitored the soil temperatures, moisture contents, CO2 concentrations and stable carbon isotopic compositions of the four soil profiles in the naturally restored region of Puding Karst Ecosystem Research Station to reveal their changes resulting from natural vegetation restoration for abandoned farmland in karst regions. The results showed that at the initial stage (herbaceous stage) of natural vegetation restoration, the initial weeds were gradually replaced with a single dominant species, with the C4 plants Imperata and Miscanthus becoming the main contributors to the vegetation biomass of the abandoned farmland. The soil profile temperature and moisture content decreased. The soil moisture content significantly decreased at a depth of 40 cm. The soil profile CO2 concentration showed both increase or decrease. During the restoration from weeds to the single species Imperata, the soil CO2 concentration increased, and the delta 13C values gradually became positive. In comparison, during the restoration from weeds to the single species Miscanthus, the soil profile CO2 concentration decreased, and the delta 13C values gradually became positive. Moreover, the increase in soil porosity enhanced the carbon exchange between the soil and the atmosphere. Dominant species slow down positive succession, and artificial interventions are needed to enhance biodiversity and ecosystem stability.

Soil-epikarst thickness and near surface characteristics are important components in understanding surface and groundwater interactions in karst environments. However, the complex lithological conditions, non-transparent rock and soil structures, and strong spatial heterogeneity limit the accurate quantification of soil thickness (ST) and epikarst thickness (EkT). In this study, we investigated the soil-epikarst structures and their spatial distribution at key topographic locations including different hillslope position, ridge, saddle, and valley using Electrical Resistance Tomography (5268 sampling points) in a peak cluster-valley catchment in Southwest China. The application of revised inflexion points in 1D resistivity vertical profiles for improving ST and EkT characterization accuracy was assessed, with interpretations validated against borehole data. The results show that compared with the interpretation accuracy of using a specific resistivity threshold at interfaces, the revised inflexion point of the 1D resistivity vertical profile significantly improved the interpretation accuracy of ST and EkT. The average ST in the valley (3.23 m) is much greater than that in hillslopes (0.49 m), while the average EkT in the valley (3.77 m) is smaller than that in hillslopes (3.93 m). The ST and EkT demonstrated a synchronous zonality variation pattern at different hillslope positions and valley. Plan and profile curvature, flow length up/down, aspect, and elevation are key topographic characteristics affecting EkT’s spatial heterogeneity. The key findings of this study contribute to advancing the accurate interpretation of soil-epikarst structures under complex lithological conditions in karst areas, and support underground structural parameters for hydrological simulation at catchment scale.

Coastal groundwater salinization induced by marine transgression, sea level rising, and/or seawater intrusion due to anthropogenic activities has been a challenge for water security worldwide. Understanding of the spatial distribution of saline water and its sources is important for the protection of fresh groundwater resources from salinization necessitates. In this study, the processes of groundwater salinization in two shallow aquifers of the North China Plain near Bohai Sea were characterized using hydrogeochemical analysis and paleohydrogeological modeling. The groundwater Cl in the shallow Aquifer I and II had the ranges of 10.2 similar to 21556 mg/L and 79.1 similar to 15800 mg/L, respectively. The distribution of groundwater isotopic signatures and chemistry, including Cl/Br molar ratio, indicates that the shallow groundwater within a distance less than similar to 60 km to Bohai Sea is affected by the marine transgression/regressions. The groundwater in Aquifer II was more widely influenced by the saline water compared to that in Aquifer I. The results of paleo-hydrogeological modeling confirmed the primary role of several events of marine transgressions in groundwater salinization. The fingering process of vertical infiltration of saline water by free convection was identified from the modeling results, which was constrained by preferential flow paths and low permeability barriers of aquitards. The modeling results show that seawater infiltration was rapid, reaching a depth of 140-160 m B.S.L.. The trend of downward permeation of shallow saline water would further threaten the groundwater quality of shallow and deep aquifers that sever as the sources of water supply in coastal area of the North China Plain.