Sediments are an important sink for heavy metal pollutants on account of their strong adsorption capacity. Elevated content of Cu was observed in the Chengdao area of the Yellow River Delta, where the surface sediment is mainly silt and is prone to be liquefied under hydrodynamic forces. The vertical transport of fine particles, along with pore water seepage, during the liquefaction process could promote the migration and diffusion of Cu from the interior of sediment. The present study involved a series of wave flume experiments to simulate the migration and diffusion of Cu from the interior of sediment in the subaqueous Yellow River Delta area under wave actions. The results indicated that sediment liquefaction significantly promoted the release of Cu from internal sediment to overlying water. The variations of Cu concentrations in the overlying water were opposite to the suspended sediment concentrations (SSCs). The sediment liquefaction caused high initial rises of SSCs, but led to a rapid decline of dissolved Cu concentration at the initial period of sediment liquefaction due to the adsorption by fine particles. Afterwards, the SSCs slightly increased and then gradually decreased. Meanwhile, the dissolved Cu concentration generally kept increasing under combined effects of intensively mix of sediment and overlying water, pore water seepage, and desorption. The dissolved Cu concentration in the overlying water during sediment liquefaction phase was 1.5–2.2 times that during the consolidation phase. Sediment liquefaction also caused vertical diffusion of Cu in sediment and the diffusion depth was in accordance with the liquefaction depth. The results of the present study may provide reference for the environmental management in the study area.

The Changjiang U ore field developed typical granite-related U mineralization in the Zhuguangshan complex, China. Pitchblende is the most important ore mineral in these mineralizations. In this study, the mineralogy and geochemistry of pitchblende were investigated by electron probe microanalysis (EPMA) and laser ablation inductively coupled plasma mass spectrometry (LA–ICP–MS) to identify the genesis of the Changjiang U ore field. Pitchblende exhibits colloidal, fragmented, spherulitic and fine-grained crystals in U ores. Its geochemical compositions are similar to those of other granite-related U deposits in South China, which have elevated contents of U, Sr, As and W; low contents of Pb, Th, Zr, Nb, Ta, Hf, Co, Ni and rare earth elements (REEs); and variable amounts of Ca, Si, Bi, Y, V and Zn. These geochemical signatures suggest that mineralization occurred through hydrothermal genesis and that the hosting Youdong and Changjiang granites acted as the dominant U sources. The uraninite in these granites might be the major U source mineral. Uranium mineralization occurred under the following conditions: low temperature (<250°C), low oxygen fugacity (log fO2=-29.5 - -25.5), weakly acidic (pH=5.3-5.9), high CO32- and F- contents and a silicon-saturated solution. Rapid changes in the physicochemical conditions of the ore-forming fluid are responsible for the precipitation of pitchblende. Combined with previous studies, we propose that U-rich granites, Cretaceous-Tertiary crustal extensions, regional faults and hydrothermal alterations were the critical factors for U formation in the Changjiang ore field.

Agricultural measures for cotton (Gossypium spp.) cultivation generally adopt a traditional and uniform management method in the reclamation area of the abandoned salt pan on the southern coast of Laizhou Bay, without considering spatial variability of the soil’s physical environment. This method might lead to overfertilization in some high-nutrient plots and poor fertilization in other low-nutrient plots, which will cause high heterogeneity of crop yields and low profits. The objectives of this study were to delineate and to assess the suitability of the resulting site-specific management zones by describing spatial variability in soil attributes and crop yields. A 4.8 ha field of reclamation area in the coast was selected as the research object. A total of 12 soil attributes representing the physio-chemical attributes of soil (0-20 cm) and aboveground biomass (AGB) of cotton on 48 sampling locations were chosen from the study area. Principal component analysis and the fuzzy k-means clustering method were used to determine optimal clustering number of the study area and identify management zones. Results showed that the number of reasonable management zones were two, and confidence levels of soil organic matter (SOM) and AGB were significantly different at a probability level p < 0.01, while total N, available N, available K, cation exchange capacity, and soil salinity showed significant differences at p < 0.05. Management zones determined based on the selected soil attributes and crop AGB provide farmers with the opportunity to perform specific site management in cotton fields to achieve precision agriculture and provide a reference for formulation of a reclamation strategy for the salt pan.

The secure and effective use of marginal water resources, such as brackish water, plays a crucial role in ensuring food security and promoting the sustainable development of agricultural land. This paper conducted indoor soil column experiments to simulate the infiltration of brackish water (0, 1, 3, and 5 g L⁻¹) in order to study the effects of infiltration on the movement of soil water and salt, aiming to address the critical challenge of utilizing marginal water resources in coastal saline-alkali areas. The result showed that, as salt content increases, the movement speed of the moisture front and soil infiltration rate gradually decrease over the same period of time. The moisture front progress and infiltration volume showed a positive correlation. The moisture content of the soil profile gradually decreased, within the soil depth range of 0–40 cm, except for the 5 g L⁻¹ saline water infiltration, and the Cl⁻ content increased, while the other treatments showed a trend of first decreasing and then increasing. The higher salt content at the same depth, the higher the Na⁺ and Cl⁻ contents. Under different irrigation water volume conditions, the soil profile conductivity shows a trend of first decreasing and then increasing. The research findings advance fundamental understanding of salinity-driven soil hydrological processes, offering theoretical support for the sustainable utilization of brackish water, balancing agricultural water demand and soil health in coastal areas.

Silty seabed sediments in the subaqueous delta of the Yellow River are heavily contaminated with petroleum-derived polycyclic aromatic hydrocarbons (PAHs). Storm-induced sediment resuspension and liquefaction are key mechanisms responsible for the remobilization of PAHs into the overlying water column. In this study, laboratory-scale wave flume experiments were conducted to simulate PAH release under three hydrodynamic scenarios: (i) static diffusion (Stage I), (ii) low-intensity wave action (5 cm wave height, Stage II), and (iii) high-intensity wave action (12 cm wave height, Stage III). Results revealed a strong positive correlation between suspended particulate matter (SPM) and PAH concentrations in the aqueous phase during sediment disturbance. In particular, sediment liquefaction significantly enhanced PAH release, with concentrations up to five times higher than those under static conditions. Furthermore, liquefaction facilitated vertical migration of PAHs within sediments, resulting in reductions in PAH levels below the original background concentrations. The release dynamics varied notably among PAH species: low-molecular-weight (2–3 ring) PAHs, with lower hydrophobicity, were primarily detected in the aqueous phase, while medium- and high-molecular-weight PAHs remained predominantly associated with sediment particles. These findings underscore the critical role of hydrodynamic disturbances—especially sediment liquefaction—in influencing PAH mobility and offer important implications for pollution risk assessment and coastal management in storm-impacted deltaic environments.

Freshwater scarcity and soil salinization limit coastal agriculture, and brackish water irrigation may help alleviate regional water shortages. This study examined the effects of irrigation water salinity on water–salt dynamics and ion distribution in coastal saline soil from Laizhou Bay. Repacked soil column experiments were conducted using a freshwater control and brackish water treatments with TDS levels of 1, 3, and 5 g L⁻¹. Soil water content and electrical conductivity were monitored at 1 min intervals at five depths, and pore water ion composition was analyzed after infiltration. Higher salinity was associated with reduced cumulative infiltration and infiltration rates, delayed wetting front migration, and longer infiltration durations. Freshwater cumulative infiltration reached 11.94 L, whereas the 3 and 5 g L⁻¹ treatments decreased final cumulative infiltration by more than 11%. Soil EC increased with salinity, with higher values occurring mainly in the middle and lower soil layers. Na⁺ and Cl⁻ were the dominant ions contributing to salinity risk and moved downward with the wetting front. Low-salinity brackish water caused less short-term infiltration inhibition and salt accumulation risk than higher-salinity water under laboratory column conditions. However, field validation, crop response evaluation, economic feasibility assessment, and long-term salt balance analysis are required before practical irrigation recommendations can be made.