With rapid developments in society and economy, the concentrations of heavy metals in surface water in South China have increased significantly, which poses a serious threat to the regional water security. In this study, the Fuhe River watershed in South China was selected as the study area to analyze physicochemical characteristics and heavy metal (Cu, Zn, Pb, Cd and Cr) concentrations in river water in the dry and rainy seasons, in 2019, with the purpose of exploring their spatial–temporal variations and main influences and assessing the potential health risks of heavy metals. The pH value of river water varied from 5.82 to 7.97, and it fluctuated less overall in the dry season, but it oscillated greatly in the rainy season and was lower, especially in the lower reach of the Fuhe River. The electrical conductivity (EC) value changed between 33 μS/cm and 128 μS/cm and increased and fluctuated along the river flow in the two periods. The concentrations of Cd, Cr, Cu, Pb, and Zn in river water showed obvious differences between the two periods. The concentrations of Cd and Cu were lower with the ranges from 0.001 μg/L to 0.67 μg/L and from 1 μg/L to 12 μg/L, respectively, in the dry season than in the rainy season, while there were inverse cases for other heavy metals. Along the river flow, the Cr concentration was stable, whereas other heavy metals showed increasing trends. It was noted that the concentrations of heavy metals in the Fuhe River were, on average, lower than the Chinese drinking standard values, with the concentration of Pb in the dry season significantly higher than the drinking standard value of the World Health Organization (WHO). Principal component analysis and correlation analysis showed that rock weathering and anthropogenic inputs were the main controlling factors of Cu and Zn in the Fuhe River, and human activities were mainly responsible for Pb, Cr, and Cd concentrations. The health risk assessment results showed that the non-carcinogenic risk (HQ_ingestion) value of Pb was greater than 1 in most sampling points in the middle and lower reaches in the dry season, suggesting a significant non-carcinogenic risk for adults and children by direct ingestion. The minimum carcinogenic risk (CR_ingestion) value of Cr was more than 10⁻⁴ in the rainy and dry seasons, and the CR_ingestion value of Cd in some sampling points was more than 10⁻⁴ in the rainy season, indicating significant cancer risks to adults and children. For areas with significant pollution and health risks in the Fuhe River watershed, it is urgent to strengthen the controls of industrial, agricultural, and urban wastewater discharge.

Understanding the phosphorus (P) cycle is essential for preventing soil P loss, improving environmental quality, and promoting sustainable agriculture, particularly in urban areas. In this study, a representative city of the lower Yangtze River Basin, Nanchang, was chosen to systematically explore the distribution and transformation of soil P forms, which were extracted by an improved SEDEX method and measured by a standard phosphorus–molybdenum blue method under three land use patterns. The contents of soil P forms were the highest in the dryland and the lowest in the paddy field, with total P accumulation in the upper wasteland and paddy field soils but in the lower dryland soil. The pH value and grain size affected soil P form distributions to a variable extent from one land use pattern to another. The transformation of soil P forms was weak in the wasteland. It was first found that some detrital limestone P (De-P) was transformed into exchangeable P (Ex-P) in the paddy field with authigenic calcium-bound phosphorus (Au-P) and organic phosphorus (OP) transformation, and the transformation between Ex-P and iron-bound phosphorus (Fe-P), Au-P, and between Au-P and OP existed in the dryland. Land use pattern was the dominant driver for the P distribution and transformation of soil P. This study highlights the critical role of land use patterns in affecting the P cycle of soils in urban areas and the importance of sustainable urban land management.

Fuhe River is the second largest river that flows into Poyang Lake, the largest freshwater lake in China. With rapid socioeconomic development, heavy metal pollution in its sediments has become increasingly severe. To clarify the distribution and sources of heavy metals in the Fuhe River Basin, sediment samples were collected from the mainstream and major tributaries in July 2021, and the contents of Cr, Mn, Ni, Cu, Zn, Cd, Pb, U, Zr and Pb isotopes in the sediments were measured. Results showed that Zr, U, and Cd contents were higher in the upper reaches; Cr was highest in the lower reaches and Ni, Cu, Zn and Pb contents peaked at the estuary of the Yihuang River (a tributary). The analyses of the multivariate statistical methods (MVSM), including Absolute Principal Component Score-Multiple Linear Regression and Positive Matrix Factorization, principal component analysis and correlation analysis, revealed that Mn, Cu, Zn and Pb were mainly from industrial activities, Cd, U and Zr were from natural rock weathering, Cr came from agricultural activities, and Ni originated from the combined pollution of industry and agriculture. Pb isotope signal highlighted that Pb in the sediments was mainly associated with industrial activities. The Pollution Load Index highlighted the most severe pollution at this estuary, while the Geo-accumulation Index indicated prominent Cd pollution (twice the background value). The Potential Ecological Risk Index and Human Health Risk Assessment Model indicated that the risks of sediments in the middle reaches are greater. These findings help to deeply understand the cycle of river pollutants and are also helpful for the treatment of river pollution.

The Jianggang sand ridges (JSR) in the southwestern Yellow Sea are a radiating tidal sand ridge system that plays crucial roles in ecological preservation, coastal protection, and terrestrial resource supply. Clay and silt fractions constitute important sediment components of the Jianggang sand ridges. In this study, the Sr-Nd isotopes of clay fractions and the Pb isotopes of K-feldspar in the silt fractions, along with their elemental geochemistry, are investigated to reveal the provenance and transport patterns of clay-size and silt-size sediments in the study areas. The results show that in both the clay-size sediments and the K-feldspar of the silt-size sediments, Ba exhibits the highest content, with the ranges of 432.24 μg/g to 531.05 μg/g and 398.02 μg/g to 2822.36 μg/g, respectively. In contrast, Lu shows the lowest abundance (<0.5 μg/g and <0.1 μg/g, respectively). The ⁸⁷Sr/⁸⁶Sr and ε_Nd(0) values of the clay fraction vary from 0.7158 to 0.7265 and from −14.65 to −10.92, respectively. The ²⁰⁶Pb/²⁰⁴Pb, ²⁰⁷Pb/²⁰⁴Pb, and ²⁰⁸Pb/²⁰⁴Pb of K-feldspar in silt fraction are 17.959~18.429, 15.450~15.689, and 38.066~38.551, respectively. Through the MixSIAR model, it is suggested that the Yangtze River Mouth is the dominant contributor to clay-size sediments in both the onshore and offshore sand ridges (53.9 ± 8.8% and 51.9 ± 8.4%, respectively), followed by the Modern Yellow River Mouth and the Old Yellow River Delta (sum of contributions: <36%). For the silt fraction, the primary sediment sources of the onshore and offshore sand ridges are the Yangtze River Mouth (46.8 ± 5.5%) and the Old Yellow River Delta (42.4 ± 5.3%), while the Modern Yellow River contributes less than 16%. The Northern Chinese Deserts and the Korean rivers make only minor contributions to both fractions. Elemental and isotopic tracers indicate that the silt-size and clay-size sediments derived from the Modern Yellow River are transported southward along the Jiangsu coast by the Subei Coastal Current. Meanwhile, the silt fraction from the Yangtze River Mouth is carried northward along the coast under the influence of the Subei Coastal Current, whereas the clay fraction of it has another longer path, which moves through the central Yellow Sea and migrates southward along the Jiangsu coast to the Jianggang sand ridges under the influence of the Yellow Sea Warm Current. This study enriches the geochemical dataset of the southern Yellow Sea.

Water quality monitoring data of rivers and lakes in the Yuanhe River Basin from 2021 to 2023 were collected to investigate the distribution characteristics and pollution influence factors of nitrogen (N) and phosphorus (P) in the water bodies. The results showed that the total phosphorus (TP) concentration in most river and lake water samples exceeded the National class Ⅰ surface water standard, and the total nitrogen (TN) concentration in all samples was greater than 0.2 mg/L, indicating a risk of eutrophication in the river-lake water. The Water Quality Index (WQI) indicates that the water quality in the Yuanhe River Basin ranges from average to excellent. The average NH₄⁺-N concentration in river and lake water accounted for 13.4% and 9.1% of TN, respectively. Principal Component Analysis (PCA) revealed that nitrogen and phosphorus concentrations in river water were mainly influenced by Point source pollution, non-point source pollution and organic matter decomposition. For lake water, the main controlling factors included Point source pollution, agricultural cultivation and livestock breeding (non-point source pollution), phytoplankton growth, and organic pollutant inputs from rainfall scouring. Results from the Absolute Principal Component Scores-Multiple Linear Regression (APCS-MLR) model further indicated: (1) non-point source pollution significantly affected river TP, with a contribution rate of 39.3%, while agricultural cultivation and livestock farming contributed up to 71.9% to lake TP; (2) Point source pollution had a notable impact on TN in both rivers and lakes, with contribution rates of 52.7% and 75.4%, respectively; (3) Unknown sources contributed the largest proportion to river and lake water at 53.3% and 18.7%, respectively, highlighting the need for further investigation.