Shenting Gang

Comprehensive monitoring of per- and polyfluoroalkyl substances (PFASs) in drinking water sources is challenging because sampling intensity, analytical coverage, reporting limits, and well construction vary among monitoring programs. We developed a machine learning pipeline to characterize environmental and pollution source susceptibility to PFAS occurrence in municipal and public supply groundwater wells across California. The assembled covariate inventory contained 7951 public supply wells; 7938 wells contributed 60,744 first-classifiable well–compound records for the eight-compound modeling analysis. Occurrence was defined as a concentration greater than 2 ng/L at the first-classifiable test for each well–compound pair. Eight compounds met prespecified support criteria: PFOS, PFHxS, PFOA, PFBS, PFHxA, PFPeA, PFBA, and PFHpA. Separate binary classifiers were evaluated using five spatially blocked folds and a forward temporal test for first-tested wells from 2024 onward. Across the eight compounds, calibrated Extra Trees achieved a mean spatial ROC-AUC of 0.722 and a forward temporal ROC-AUC of 0.669. Mean PR-AUC was 0.350 for spatial validation (mean positive rate, 16.2%) and 0.223 for forward temporal validation (mean positive rate, 9.6%), which indicates moderate discrimination that supports ranking wells for confirmatory sampling but not classifying individual wells. The spatial ensemble generated 1 km screening surfaces for PFOS, PFOA, and PFHxS with explicit model support and extrapolation diagnostics. These surfaces represent susceptibility under a typical public supply well scenario and are intended to prioritize confirmatory monitoring, not establish contamination at unsampled wells, attribute occurrence to specific facilities, or validate 1 km positional accuracy.

To clarify the distribution pattern of the fault-karst groundwater flow system in the Baotu Spring Basin, Shandong Province, China, and to reveal the controlling mechanisms of groundwater flow and the response characteristics of solute transport, this study focused on the Cambrian-Ordovician carbonate rock distribution area within the basin. Karst water, pore water, and surface water samples were collected, and a comprehensive research approach was employed, integrating hydrochemical analysis, statistical analysis, and numerical simulation based on FEFLOW. The results indicate that calcium ions (Ca²⁺) are the dominant cations in the water bodies of the study area, with bicarbonate ions (HCO₃⁻) and sulfate ions (SO₄²⁻) as the primary anions. The average total dissolved solids (TDS) concentrations of karst water, pore water, and surface water are 570.73 mg/L, 746.96 mg/L, and 507.75 mg/L, respectively. The low coefficient of variation in ion concentrations reflects the overall stability of water quality across the study area. Hydrochemical characteristics are predominantly governed by rock weathering, with negligible influence from evaporation-crystallization processes, while atmospheric precipitation exerts a dilution effect. Calcite and dolomite are in a supersaturated state, whereas gypsum and halite are prone to dissolution. Verification results of the groundwater flow numerical model demonstrate that the selected hydrogeological parameters and source-sink terms are reasonable, enabling accurate characterization of the overall groundwater flow field, which flows from southeast to northwest in the study area. Fault zones significantly complicate groundwater flow paths: the Qianfoshan Fault induces flow-line deflection, while the Chaomidian Fault triggers flow-line convergence due to its high permeability. Using nitrate ions (NO₃⁻) as a tracer, this study confirms that fault permeability coefficient and time exert a significant regulatory effect on solute transport and pollution plume distribution. Under the dominance of fault-controlled permeability mechanisms, the pollution plume’s influence range expands dynamically over time as long as a hydraulic head difference persists. This study systematically clarifies the key evolutionary processes and core controlling factors of the fault-karst groundwater flow system in the Baotu Spring Basin, further enriches the theoretical system of hydrogeological research in karst areas of northern China, and provides reliable theoretical support and practical basis for the refined management of regional water resources, ecological protection, and sustainable development.

Karst groundwater is an important water supply, especially in northern China. With the rapid development of China’s economy, anthropogenic activities have had a significant impact on karst groundwater formation, circulation and other processes. In this paper, the Baotu spring basin, which is closely related to anthropogenic activities, was selected as the research object to carry out a study of water chemical characteristics and evolutionary processes. And, mathematical statistics, Piper trilinear diagram, Gibbs diagram, and ion ratio methods were used to analyze the characteristics and evolution processes of groundwater. The results of this study show that the hydrogeochemical components of karst groundwater are mainly controlled by the weathering of rocks, mainly by the dissolution of carbonate rocks and silicates with the dominant cation of Ca²⁺ and the dominant anion of HCO₃⁻. Considering the role of anthropogenic activities, including agricultural and industrial activities, the evolution process of karst groundwater is mainly controlled by hydrogeochemical effects such as mineral dissolution and filtration, the mixing of multiple water bodies, anthropogenic activities (domestic sewage, industrial and agricultural wastes), oxidation–reduction and cation alternating adsorption. Moreover, the influence of anthropogenic activities on the formation and evolution of karst groundwater gradually increases, leading to the rise in nitrate content in karst groundwater and accelerating carbonate rock dissolution. The research results of this paper can provide a favorable reference for environmental protection and research on karst groundwater in areas of intensive anthropogenic activity.

Environmental nanoparticles are known to be present in various aquatic environments, exerting significant influences on water quality, particularly in water distribution systems. However, there has been a notable dearth of research on the presence and impact of environmental nanoparticles in mineral water, a unique water resource. In this study, we employed Nanoparticle Tracking Analysis (NTA) and conducted High-Resolution Transmission Electron Microscopy (HRTEM) to address this research gap. This groundbreaking study represents the first comprehensive exploration of environmental nanoparticles within natural mineral water from Zibo City, Shandong Province, China. The results of the NTA showed that the concentration of the particles was 5.5 × 10⁵ particles/mL and the peak diameter of the size distribution was 180 nm. The HRTEM showed that the nanoparticles were granular, pinniform, rodlike, and flakey in shape, and some of the nanoparticles existed in aggregation. The energy-dispersive spectrometry results showed that most of the nanoparticles contained O, Mg, Ca, Si, Fe, Ti, and P, and some of them also contained F, V, S, and Mn. When combined with the characteristics of the selected area electron diffraction pattern, the nanoparticles were confirmed to be Ca-bearing nanoparticles, attapulgite nanorods, MnO₂ nanosheets, and TiO₂ nanoparticles. These findings shed light on a novel manifestation of elemental compositions in mineral water. Furthermore, considering the chemical and physical attributes of both the nanoparticles and mineral water, it is highly plausible that these environmental nanoparticles result from the weathering of minerals. The presence of these nanoparticles within mineral water offers a unique opportunity to advance our comprehension of nanoparticle behavior across diverse systems. Significantly, the realm of environmental nanoparticle science holds paramount importance for ongoing endeavors in ensuring water safety, enhancing treatment processes, and facilitating effective remediation procedures.

Environmental nanoparticles have been shown to exist in most aquatic environments, and environmental nanoparticles in water distribution systems significantly affect water quality. However, little research has been conducted on the environmental nanoparticles in mineral water, which is a special water resource. Nanoparticle tracking analysis (NTA) and high-resolution transmission electron microscopy (HRTEM) were conducted. This study was the first to identify many environmental nanoparticles in natural mineral water in Zibo City, Shandong Province, China. The results of the NTA showed that the concentration of the particles was 5.5 ×106 particles/mL and the peak diameter of the size distribution was 180 nm. The HRTEM showed that the nanoparticles were granular, pinniform, rodlike, and flakey in shape, and some of the nanoparticles existed in aggregation. The energy-dispersive spectrometry results showed that most of the nanoparticles contained O, Mg, Ca, Si, Fe, Ti, and P, and some of them also contained F, V, S, and Mn. When combined with the characteristics of the selected area electron diffraction pattern, the nanoparticles were confirmed to be Ca-bearing nanoparticles, attapulgite nanorods, MnO2 nanosheets, and TiO2 nanoparticles. These results indicate a new form of elements occurring in mineral water. In addition, based on the chemical and physical characteristics of the nanoparticles and mineral water, these environmental nanoparticles in the mineral water are likely to be the weathering byproducts of minerals. These nanoparticles within mineral water provide a good opportunity for understanding the behavior of nanoparticles in varied systems. Moreover, environmental nanoparticle science is important for continuing efforts in water safety, treatment, and remediation.

Reduction in river discharge and sediment load has left deltaic lobes in the world’s many river deltas starving, but knowledge of how the subaqueous topography of these abandoned subdeltas responds to environmental changes is limited. In this study, we aimed to determine the long-term dynamics of the subaqueous seabed of abandoned delta lobes to advance current knowledge. As a case study, we selected an abandoned subdelta on the Yellow River Delta of the Bohai Sea, China, for which three-decade long (1984–2017) bathymetric data and long-term river discharge and sediment load records are available. We analyzed the seafloor surface change and quantified the void space from the sea water surface to the seafloor. In addition, we surveyed the seafloor surface with an M80 unmanned surface vehicle carrying a multibeam echo sounder system (MBES) in 2019 to obtain high-resolution microtopography information. We found that a net volume of 5.3 × 10⁸ m³ of sediment was eroded from the study seabed within an area of 3.6 × 10⁸ m² during 1984–2017. This volumetric quantity is equivalent to 6.89 billion metric tons of sediment, assuming a bulk density of 1.3 t/m³ for the seabed sediment. The seabed erosion from 0 to −5 m, from −5 to −10 m, and below −10 m has showed a similar increasing trend over the past 33 years. These findings suggest that seabed erosion in this abandoned subdelta will very likely continue, and that other abandoned delta lobes in the world may have been experiencing similar seabed erosion due to the interruption of the sediment supply and sea level rise. It is not clear if the seabed erosion of abandoned delta lobes would have any effect on the stability of the coastal shoreline and continental shelf.

The coastal area is a major area of socio-economic development and the most active zone for human activities. With the rapid development of the economy and the strengthening of urban construction, the groundwater environmental problems in coastal areas are increasingly prominent. It is significant to investigate the groundwater chemical characteristics, hydrochemical types, and the factors that influence groundwater chemistry for water resources protection and groundwater resources development. In this paper, 48 groundwater samples and 5 surface water samples from the study area were analyzed with statistical analysis, Piper diagram, Gibbs diagram, mineral saturation index method, and the ionic scale factor, and explored the factors that influence groundwater chemistry. The modified Nemerow index method was also applied to evaluate the groundwater. The results show that the groundwater in the study area is neutral to weakly alkaline (average pH = 7.0~8.0). The groundwater chemical types are mainly Cl·SO₄-Na and SO₄·Cl-Ca·Mg. Hydrochemistry is mainly influenced by rock weathering and evaporative concentration. TDS was strongly correlated with TDS, Na+, Mg²⁺, K⁺, Ca²⁺, Cl⁻, SO₄²⁻, and the saturation index showed a gradual increase along the groundwater drainage flow path, it indicates that the main groundwater ions originate from the dissolution of halite, sulfate, and carbonate. Combining GIS technology and the kriging spatial interpolation method, we obtained the current situation map of groundwater quality in Laoshan District. The groundwater quality is mainly III water, and the overall water quality is good; IV and V water is mainly distributed in the middle and lower reaches of rivers, distributed in a belt pattern along the coastline. It is mainly influenced by both the human factor and seawater intrusion. It is significant for the utilization of groundwater resources and the management of seawater intrusion in the Laoshan District. In addition, the proposed research ideas and methods provide a reference for the study of groundwater genesis in other coastal areas in the world.