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Rare-earth elements are widely used in the study of source tracing and geochemical characteristics, which can reflect the degree of influence of human activities on water environment. In order to reveal the additive effects of various human activities on the geochemical characteristics of rare-earth elements in the surface water environment, the content of rare-earth elements in the river in the coal grain composite area of eastern China was determined by inductively coupled plasma mass spectrometry (ICP-MS). The results showed that all water samples were alkaline, ΣREE content ranged 0.18–0.88 μg·L−1, with an average value of 0.28 μg·L−1. All the water samples showed significant enrichment of light rare-earth elements due to a combination of natural processes and external inputs. The spatial distribution and fractionation characteristics of rare-earth elements show that rare-earth elements (especially Ce) are prone to adsorption/complexation reactions with colloidal particles, resulting in their removal from rivers, Eu anomaly is related to plagioclase crystallization and human activities (coal development, agricultural production, urbanization process), and Gd anomaly is only related to human activities. The research results can provide scientific reference for revealing the distribution of rare-earth elements and geochemical environmental behavior in rivers environment under the superimposed influence of various human activities. [ABSTRACT FROM AUTHOR]

Some seriously weathered jades of Fubin culture were unearthed at the Moyishan site in Lingnan, South China. These long-buried jades have many secondary changes such as discoloration, microstructural change and chemical composition variation. To explore the formation mechanism of secondary changes, the microstructure, mineral components, and chemical content of the jade samples and their buried soil are analyzed separately. The jade with red-brown shell is preserved well and shows better structural stability, further research indicates that it's the result of surface complexation reactions. During the long-term burial in acidic soil environment, the jade wrapped in the negatively charged kaolinite which absorbed Fe3+ to complexed on the jade surface. Iron(ⅲ) precipitates causes the dense shell to appear red-brown. [ABSTRACT FROM AUTHOR]

Sediment, consisting of different aggregation fractions, is a hotspot site for transport and transformation of various pollutants including antibiotics. However, the fate of different antibiotics in aquatic sediments mediated by sediment aggregation fraction adsorption and the mechanism behinds are still unclear. In this study, we investigated the adsorption behavior of two fluoroquinolone antibiotics (ciprofloxacin and ofloxacin) on four aggregation fractions separated from the sediment of Taihu Lake, a typical lake contaminated by antibiotics in China. The results showed that the adsorption of ciprofloxacin and ofloxacin fitted the Freundlich model, irrespective of sediment aggregation size. The adsorption of ciprofloxacin and ofloxacin was depended on the size of sediment aggregation fractions, and the macroaggregation (> 200 μm) exhibited the strongest capacity, followed by large microaggregation (63–200 μm), medium microaggregation (20–63 μm), and small and primary microaggregation (< 20 μm). This fraction size-dependent effects of sediment aggregations on antibiotic adsorption might be closely related to the differences in their specific surface areas, organic matter contents, and surface functional groups. The adsorption of ciprofloxacin and ofloxacin by sediment aggregation fractions was characterized by a combination of chemical and physical adsorptions, with the former being the dominant process. Compared with ofloxacin, ciprofloxacin could be more rapidly and easily absorbed by four sediment aggregation fractions, and more readily complexed with carboxyl groups on macroaggregation surface. The adsorption of two antibiotics by extracellular polymeric substance showed that tryptophan and tyrosine protein-like, humic-like substance on the surface of sediment could bind to both antibiotics through a complexation reaction. The π-π electron donor–acceptor interaction and hydrogen bonds were responsible for the antibiotic adsorption by sediment aggregation. [ABSTRACT FROM AUTHOR]

[Display omitted] • The mobilization of As is closely related to Fe minerals and OM during irrigation. • OM introduced by the irrigation affected As and Fe behavior. • Ternary complexation of As-Fe-OM compounds influence As mobilization during irrigation. • Terrestrial OM promotes As-Fe-OM complexation reactions during irrigation. Organic matter (OM) plays an important role in the biogeochemical transformation of arsenic (As) in groundwater and sediments. High-As groundwater used for irrigation introduces dissolved As into the ground. Moreover, water table fluctuations and variations in redox conditions affect As mobilization in both the unsaturated and saturated zones. A field experiment was conducted at the DY site, Datong Basin, China to explore the effect of OM on As and iron (Fe) mobilization and transformation in the unsaturated and saturated zones during irrigation. Soil water/groundwater and sediments sampled at different depths during the experiment were analyzed to investigate the hydrochemical processes and correlations between As, Fe, and OM concentrations. Irrigation activities led to the accumulation of aqueous As in the saturated zone and increasing As content in the topsoil. Analyses of Fourier-transform infrared (FTIR) spectra suggest the existence of As-Fe-OM ternary complexation. Parallel factor analysis (PARAFAC) of the three-dimensional fluorescence excitation–emission matrix (EEM) reveals that water-extractable organic matter (WEOM) of sediments comprises three major components, two terrestrial humic-like components (C1 and C2) and one protein-like component (C3). And terrestrial humic-like components with high molecular weight promotes As-Fe-OM complexation reactions. The results of this study demonstrate As mobilization under irrigation conditions and contribute to a better understanding of the role of OM under high-As groundwater irrigation. This study has implications for controlling and managing OM or As-contaminated water for irrigation in high-As groundwater regions. [ABSTRACT FROM AUTHOR]