Bin Yan

Microplastics (MPs) synergistically interact with heavy metal contaminants, posing substantial ecological threats to biota. Hydrodynamic regimes and water-level fluctuations within the Three Gorges Reservoir (TGR) critically influence contaminant dynamics. Nevertheless, biomolecular responses to MP and heavy metal co-exposure at protein and enzymatic levels remain inadequately characterized. This study selected polyethylene (PE), polypropylene (PP), and lead(II) ions (Pb2+) to examine the freshwater microalgae Chlorella vulgaris within the TGR. After 96 h of exposure, the half-maximal effective concentrations for PE and PP against C. vulgaris were determined to be 334 mg/L and 295.29 mg/L, respectively. PE, PP, and Pb2+ significantly reduced the accumulation of C. vulgaris biomass, deteriorated algal cell growth, and caused the algal cells to undergo membrane lipid peroxidation. Nitrate and phosphate assimilation were considerably inhibited across all treatments, with heightened suppression under co-exposure. MPs’ addition significantly increased malondialdehyde levels. MP adsorption of Pb2+ appeared to attenuate Pb2+-associated changes in nitrate reductase (NR) and alkaline phosphatase activities. This study provides a theoretical foundation for evaluating MP and heavy metal ecological risks in reservoir ecosystems.

CO₂ is the main cause of the dramatic increase in greenhouse gases, posing a serious threat to human systems and ecosystems. Most existing studies focus on estimating carbon emissions and carbon sequestration, and there are relatively few studies on the quantitative analysis of CO₂ uptake by vegetation. Therefore, this paper constructed a Carbon Uptake Index (CUI) model based on the carbon estimation model and the Vegetation Carbon sequestration (VCs) model. It was used to estimate the distributional characteristics of carbon absorption in China from 2000 to 2020. Then, the inter-annual variation and spatial aggregation characteristics of carbon absorption were analyzed using linear regression models and spatial autocorrelation, respectively. The results show that from 2000 to 2020, China’s carbon uptake as a whole is in an absorptive state, with significant spatial correlation. Inter-annual variability shows an overall decreasing trend, dominated by a slight decreasing trend. The spatial characteristics of carbon absorption are mainly aggregated, with low-low aggregation in the western part of China and high-high aggregation in the southern part. The results of this paper will provide a reasonable reference for China to achieve carbon peak and carbon neutrality.

Previous investigations on heavy metals in the water–sediment compartment focused on their spatial distribution, and the influence of sediment pH and organic matter (OM) on metal environmental occurrences. However, there are limited studies on the effects of physicochemical properties on the migration and transformation of heavy metals in the water–sediment compartments. This study investigated the relationship between the physicochemical properties of sediments and the distribution and chemical speciation of heavy metals, and the potential environmental risk of heavy metals in water and sediment using Risk Assessment Code (RAC) values and the Tessier five-step extraction method. Adsorption and desorption experiments showed that the sediment had weak adsorption and the strongest desorption capacity for Cd. Results of the pH, OM, surface element content, and X-ray diffraction (XRD) patterns suggested that cadmium (Cd) was more likely to partition into the water phase from the sediment during the flooding and water storage periods. When pH was 7–8 and OM content was 3.6–5.9%, the sediment–water distribution coefficient of Cd was low due to its large ionic radius, and the surface adsorption sites were saturated by other elements. These studies can provide a theoretical basis for the management and pollution control of the Three Gorges Reservoir.

With the accelerated urbanization and rapid development of the industrial and agricultural sectors, concern about the pollution of water environments is becoming more widespread. Algal blooms of varying sizes are becoming increasingly frequent in lakes and reservoirs; temperatures, nutrients, heavy metals, and dissolved oxygen are the factors that influence algal bloom occurrence. However, knowledge of the combined effect of heavy metals and temperature on algal growth remains limited. Thus, this study investigated how specific concentrations of heavy metals affect algal growth at different temperatures; to this end, two heavy metals were used (0.01 mg/L Pb²⁺ and 0.05 mg/L Cr⁶⁺) at three incubation temperatures (15, 25, and 30 °C) with the alga Chlorella sp. A higher incubation temperature contributed to a rise in soluble proteins, which promoted algal growth. The density of algal cells increased with temperature, and catalase (CAT) decreased with increasing temperature. Chlorella sp. growth and catalase activity were optimal at 30 °C (algal cell density: 1.46 × 10⁷ cell/L; CAT activity: 29.98 gprot/L). Pb²⁺ and Cr⁶⁺ significantly promoted Chlorella sp. growth during incubation at 25 and 30 °C, respectively. At specific temperatures, 0.01 mg/L Pb²⁺ and 0.05 mg/L Cr⁶⁺ promoted the production of soluble proteins and, hence, the growth of Chlorella sp. The results provide a useful background for the mitigation and prevention of algal blooms.