As carbon intensity (CI) can better reflect the coordinated relationship between carbon emissions and economic growth, the related research has gradually increased in recent years. To better explore the influence of production technology and spatial variations on CI disparities in China, this paper constructs a dynamic spatial–temporal production-theoretical decomposition analysis (DST-PDA) model to explore the dynamic spatial disparities and temporal variations of driving factors on CI in different regions. Moreover, this paper further investigates the impact of production-related factors, such as carbon emission technology’s change with regard to carbon intensity, and explores the benchmarking catch-up effect and the effort on reducing CI by setting benchmarks and dynamic comparative analysis, which could provide guidance for some underperforming regions. The main results are as follows: (1) The overall trends of CI increased from 2007–2019, and the northwest region had the largest growth rate. (2) Energy intensity was the dominant driver to reduce CI, and technological changes also played a great role in decreasing CI. Conversely, carbon emissions efficiency had negative effects on reducing CI. (3) The spatial variations of the contributions in factors to reduce CI have gradually increased. Resource-dependent development areas have great potential to reduce carbon intensity by improving energy and carbon emission efficiencies. The northwest has great potential to reduce CI by introducing advanced technologies. Some policies are proposed based on the results.

Engineered nanomaterials are widely used in environmental remediation, agriculture, and industrial applications owing to their large specific surface area, high reactivity, and tunable physicochemical properties. However, their release into aquatic environments has raised increasing concerns regarding potential risks to primary producers. Microalgae are highly sensitive to environmental stressors and play essential roles in photosynthesis, nutrient cycling, carbon fixation, and aquatic food-web stability, making them important model organisms for assessing the toxicity of engineered nanomaterials. This review summarizes the toxic effects and mechanisms of representative engineered nanomaterials, including metal and metal oxide nanoparticles, nanoplastics, and carbon-based nanomaterials, on microalgae. Major toxic pathways include nanoparticle attachment and aggregation on algal surfaces, shading effects, membrane damage, altered permeability, cellular internalization, toxic ion release, reactive oxygen species overproduction, photosynthetic inhibition, and metabolic disturbance. The review further discusses how particle size, morphology, surface coating, dissolution, aging, light, pH, and natural organic matter regulate nanomaterial bioavailability and toxicity. Combined toxicity caused by coexisting nanoparticles or emerging pollutants is also considered, with emphasis on synergistic, antagonistic, and concentration-dependent effects. Finally, recent methodological advances, such as near-native imaging, Raman-based spectroscopy, particle-specific elemental analysis, and multi-omics approaches, are highlighted. This review provides an integrated perspective for understanding nanomaterial toxicity to microalgae and supports future ecological risk assessment in aquatic environments.