Hualong Hong

Oxygen supply and consumption create heterogeneous rhizosphere environments that regulate microbial activity and biogeochemical transformations. This study combines bibliometric analysis with a synthesis of representative research to characterize the development of this field. A screened collection of 2459 Web of Science publications from 1980 to 2026 was analyzed using publication statistics, collaboration networks, author–keyword co-occurrence, and burst detection. Annual output increased overall, with an intervening period of fluctuation and renewed expansion after 2010. China, the United States, and Germany were the leading contributors. The keyword network resolved six interconnected themes encompassing symbiotic nitrogen fixation, rice-associated microbial communities and contaminants, wetland aeration and methane processes, rhizosphere nutrient and redox transformations, constructed-wetland nitrogen removal, and reactive oxygen species and root exudates. Recent bursts in microbial community and reactive oxygen species, together with work on root exudates and iron plaque, highlight growing attention to the biological regulation of rhizosphere processes. The mechanistic literature shows that roots can act as oxygen sources or sinks, and that the consequences for carbon, nitrogen, and contaminant transformations depend on substrate supply and the spatial and temporal arrangement of redox microsites. Linking oxygen imaging with isotope tracing, microbial functional experiments, and field-scale flux measurements offers a route to connect these microsite processes with ecosystem outcomes.

Natural archives record environmental change over timescales that instrumental series cannot reach, and global environmental assessments rest on the evidence they supply. To our knowledge, however, where that evidence is produced, and whether it reflects the processes it describes, has not been established. Here we reconstruct the sampling and publication geography of 33,145 studies of past environments, tracing each to the Sustainable Development Goals it addresses. Sampling and publication are not decoupled but nearly isomorphic. Twenty-six countries account for 89% of publication credit and 81% of sampling, and all eleven goals with evidence flows draw 82–90% of their evidence from them. Those countries hold 57.5% of world population and produce that evidence roughly 28 times more intensively per head. National income acts on research output as a threshold rather than a gradient. Below about 41,000 PPP dollars per head additional income buys no additional output, while above it output rises steeply with income. Because credit and sampling are read from affiliations and abstracts, the analysis captures where research is led rather than the provenance of every sample. The evidence base for global goals therefore reflects the research geography of a minority rather than the distribution of the processes being measured. Our findings provide the first baseline against which commitments to widen participation can be measured, and identify analytical capacity, rather than access to samples, as the binding constraint on whose evidence the planet is studied.

The environmental fate of combustion-derived dissolved organic matter (CDOM) at clay mineral interfaces remains poorly understood. We applied FT-ICR-MS, XPS, and other techniques to investigate the interfacial behavior of CDOM from coal, charcoal, pinewood, and maize straw on kaolinite and montmorillonite. Two distinct mechanisms were identified: ligand exchange on kaolinite (increasing binding energies by 1.2 ∼ 1.7 eV) and Ca2+/Mg2+-mediated cation bridging on montmorillonite (decreasing binding energies by 0.3 ∼ 1.8 eV). Maize straw-CDOM and charcoal-CDOM exhibited the highest adsorption on both clays, while pinewood-CDOM showed mineral-selective retention (montmorillonite only) and coal-CDOM showed negligible adsorption. Coal-CDOM (−SO3H-rich) with negligible adsorption was due to electrostatic repulsion and hydration steric hindrance. Pinewood-CDOM (phenolic) was retained only on montmorillonite via cation bridging, as its phenolic groups cannot undergo ligand exchange with kaolinite. Charcoal-CDOM (−NH2-rich) was retained on both clays primarily through electrostatic attraction of –NH3+, with additional contributions from Ca2+/Mg2+-mediated cation bridging and cation–π interactions on montmorillonite. Maize straw-CDOM (mixed –COOH, –NH2, –SO3H) was retained through synergistic ligand exchange, cation bridging, and electrostatic/H-bonding. Concentration-dependent fractionation shifted from H-bonding/electrostatic attraction (small polar molecules) to hydrophobic/cation–π interactions (large aromatic molecules) with increasing concentration. This framework provides mechanistic context for pyrogenic carbon sequestration and contaminant mobility in clay-rich environmental matrices.

While understanding the drivers of river water quality is crucial, the dependence on ground observations hinders the accurate quantification of driver thresholds, as well as the scale-dependent effects of buffer zones. By transcending the limitations of ground observations, satellite remote sensing provides the spatially continuous data required to define effective buffer zones and determine the threshold intervals for natural and anthropogenic drivers, effectively promoting sustainable watershed management. Herein, we determined the total nitrogen (TN), total phosphorus (TP), permanganate index (COD_Mn), and turbidity in the Minjiang River of Fujian Province by synergizing Sentinel-2 imagery and in situ data (2021–2024). Subsequently, we further employed generalized additive models (GAMs) considering scale-dependent (50 m to 20 km) characteristics to screen and evaluate the natural–anthropogenic factors influencing the water quality indicators. The GAMs revealed that TN exhibited multiphasic responses to forest cover and water area, characterized by alternating positive and negative effects across their range. TP was found to be predominantly driven by agricultural and urban land use, showing clear scale–threshold effects. This study provides an integrated framework that moves beyond retrieval to quantitatively assess the impact of multi-scale natural–anthropogenic factors, offering actionable insights for precise watershed zoning and science-based management for the sustainable development of river systems.