Volume 1 Issue 1 (2025)

This study investigates the geochemical characteristics, sources, and environmental risks of heavy metals (As, Cd, Cr, Cu, Hg, Ni, Pb, Zn) in urban topsoil (0–20 cm) from three industrialized cities (Wuhan, Changsha, Xiangtan) in the Yangtze River Middle Reaches, Central China. A total of 324 topsoil samples were collected across industrial, residential, commercial, and green space areas between 2021–2023. Results show that Cd, Pb, Zn, and Cu concentrations exceed local background values by 2.3–7.8 times, with industrial areas having the highest contamination levels. Multivariate statistical analysis and positive matrix factorization (PMF) identify four primary sources: industrial emissions (38%), traffic activities (27%), agricultural inputs (21%), and natural weathering (14%). Environmental risk assessment indicates moderate to high ecological risk in industrial zones (RI=320–480) and low to moderate risk in residential/commercial areas (RI=120–240). Cd and Hg pose the greatest non-carcinogenic and carcinogenic risks to human health, particularly for children. This study provides critical insights for heavy metal pollution control and soil environmental management in industrialized urban regions.

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This study investigates the geochemical behavior, provenance, and environmental significance of rare earth elements (REEs) in surface sediments (0–10 cm) from 42 sampling sites across the Mekong River Basin (MRB). Samples were collected between 2021–2023, covering the upper, middle, and lower reaches, including mainstream and major tributaries. REE concentrations (ΣREE) range from 18.7 to 126.3 mg/kg, with an average of 64.2 mg/kg, generally lower than upper continental crust (UCC) values. Chondrite-normalized REE patterns exhibit light REE (LREE) enrichment (LaN/YbN=3.2–8.7), weak negative Eu anomalies (Eu/Eu=0.72–0.94), and flat heavy REE (HREE) distributions. Provenance analysis indicates that sediments are predominantly derived from felsic igneous rocks in the Tibetan Plateau and Indochina Peninsula, with minor contributions from mafic rocks. Weathering indices (CIA, CIW) and REE ratios (La/Sm, Gd/Yb) suggest moderate chemical weathering in the upper reaches and intense weathering in the lower reaches. Anthropogenic disturbance (mining, agriculture, dam construction) is identified as a key modifier of REE distributions in middle and lower reaches, with elevated LREE concentrations and altered Eu anomalies. This study provides new insights into REE geochemical dynamics in large river basins, supporting environmental monitoring and sustainable management of the MRB.

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This comprehensive study investigates the geochemical controls on arsenic (As) mobility in groundwater and sediments from the Ganges-Brahmaputra-Meghna (GBM) Delta, one of the world’s largest arsenic-affected regions. A total of 216 groundwater samples and 108 sediment cores (0–30 m depth) were collected from 72 sampling sites across Bangladesh and West Bengal (India) between 2021–2023. Groundwater As concentrations range from 0.01 to 586 μg/L (average=83.4 μg/L), with 78% of samples exceeding the WHO drinking water guideline (10 μg/L). Sediment As concentrations vary from 2.3 to 48.7 mg/kg (average=15.6 mg/kg), predominantly associated with iron (Fe)-oxyhydroxides (42%), organic matter (OM) (28%), and sulfide minerals (19%). Geochemical analyses reveal that As mobility is primarily controlled by reductive dissolution of Fe-oxyhydroxides, driven by microbial decomposition of OM in anoxic conditions (Eh < -100 mV, pH=6.5–8.2). Secondary controls include pH-dependent sorption, competitive anion exchange (PO₄³⁻, HCO₃⁻), and sediment mineralogy (clay content, calcite abundance). Stable sulfur isotopes (δ³⁴S) of sediment sulfides (-12.8‰ to 4.3‰ VCDT) confirm microbial sulfate reduction as a key process for As sequestration. Human health risk assessment indicates high non-carcinogenic (hazard quotient >1) and carcinogenic (carcinogenic risk >10⁻⁴) risks for 92% of the study population. This study identifies geochemical proxies (Eh, Fe²⁺, OM content, PO₄³⁻) for As-rich groundwater and proposes context-specific remediation strategies, including Fe-oxide amended filters and managed aquifer recharge. The findings provide critical insights for sustainable groundwater management in arsenic-affected deltaic regions globally.

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This study investigates the geochemical characteristics of carbonates (mineralogy, major/trace element composition, stable isotopes) in surface sediments (0–15 cm) from 56 sampling sites across the Mediterranean Sea. Samples were collected between 2021–2023, covering the Western, Central, and Eastern Mediterranean sub-basins. Carbonate content ranges from 12.3% to 78.6% (average=45.8%), dominated by calcite (65–92%) and minor aragonite (5–25%) and dolomite (3–10%). Stable carbon (δ¹³C) and oxygen (δ¹⁸O) isotopes range from -2.8‰ to 1.5‰ (VPDB) and -4.2‰ to 0.8‰ (VPDB), respectively, reflecting mixed biogenic and detrital carbonate sources. Trace element ratios (Sr/Ca, Mg/Ca, Mn/Ca) indicate temperature-dependent fractionation in biogenic carbonates and detrital input from riverine and aeolian sources. Anthropogenic carbonate input (e.g., concrete particles, shell fragments from aquaculture) is identified in coastal areas, characterized by elevated Sr/Ca ratios (0.015) and anomalous δ¹³C values (1.0‰). Paleoenvironmental reconstruction suggests Holocene sea surface temperature variations of 2–4°C and salinity fluctuations of 1–2 psu. This study provides a baseline for carbonate geochemistry in the Mediterranean, supporting paleoenvironmental research and monitoring of anthropogenic impacts on coastal sediment systems.

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This study investigates the geochemical signatures of hydrothermal fluids in surface sediments (0–20 cm) from 48 sampling sites along the Mid-Atlantic Ridge (MAR), covering the North Atlantic (20°N–45°N), Equatorial Atlantic (0°–10°S), and South Atlantic (20°S–40°S) segments. Samples were collected between 2021–2023 using remotely operated vehicles (ROVs). Hydrothermal anomalies are identified by elevated concentrations of chalcophile elements (Cu, Zn, Pb, Au), lithophile elements (Li, B, As), and rare earth elements (REEs), with ΣREE ranging from 32.6 to 189.4 mg/kg (average=87.3 mg/kg). Stable sulfur isotopes (δ³⁴S) of sulfide minerals range from -4.2‰ to 6.8‰ (VCDT), reflecting mixed mantle-derived (magmatic) and seawater sulfur sources. Trace element ratios (Li/Y, B/Nb, Zr/Hf) indicate that hydrothermal fluids are derived from partial melting of a depleted mantle with minor enriched mantle components. Seafloor mineralization associated with hydrothermal activity is characterized by sulfide-rich zones (Cu-Zn-Pb sulfides) and oxide-rich zones (Fe-Mn oxides), with Au concentrations reaching up to 2.8 ppm in mineralized sediments. This study provides new insights into mantle composition and hydrothermal processes along the MAR, supporting exploration for seafloor mineral resources and understanding of oceanic crust formation.

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