环境科学与技术最新文献

Subtropical coastal bays significantly mediate land-ocean carbon fluxes, yet their responses to concurrent warming and intensified river discharge remain unclear. Using monthly observations over a decade in Xiamen Bay and integrating flow cytometry, high-throughput sequencing, Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS), and NanoSIMS carbon tracing, we explored how microbially driven carbon cycling responds to these dual forces. Our findings reveal that under present-day conditions, a +4 °C warming would increase the abundances of Synechococcus (∼19%) and microeukaryotic algae (∼5%), suggesting an enhanced potential for labile dissolved organic matter (LDOM) production. NanoSIMS experiments showed a 5-fold increase in heterotrophic bacterial assimilation of phytoplankton-derived carbon at elevated temperatures (30 °C versus 22 °C). Concurrently, intensified riverine discharge delivered terrestrial recalcitrant DOM (RDOM), altering DOM molecular composition and decreasing overall bioavailability. These combined stressors restructured microbial communities, accelerating heterotrophic carbon processing and reducing the ratio of ecologically persistent DOM to recalcitrant dissolved black carbon. We propose a Dual-DOM Forcing framework that formalizes how thermal (autochthonous LDOM) and hydrological (allochthonous RDOM) drivers jointly regulate microbial carbon processing, DOM persistence, and coastal carbon sequestration potential. This framework provides a transferable basis for assessing the vulnerability of coastal blue carbon sinks to concurrent warming and altered river discharge.

Black carbon in seasonal snow (BCS) critically influences the Earth system by reducing surface albedo (snow darkening), perturbing radiative balance, and accelerating snowmelt. However, its climatic and hydrological impacts remain poorly quantified because high-quality data sets are scarce. This study introduces a novel Dual Random Forest (DRF) framework that synergistically constrains BCS concentration estimates through both physical mechanisms and observational fidelity. By pretraining with six spatiotemporally complete Earth System Model (ESM) simulations, driven by multisource reanalysis data, and fine-tuning against global field observations, the DRF generates a 44-year (1981-2024) global monthly BCS data set at 0.5° × 0.625° resolution. This data set achieves higher accuracy in BCS patterns and concentrations compared with observations (spatial correlation R = 0.92; normalized mean error NME = 31%), outperforming both single-constrained machine learning approaches (ESM- or observation-only) and traditional methods (CMIP5, CMIP6, and MODIS; R = 0.07-0.82, NME = 51%-1951%). It also excels in capturing seasonal variations and long-term annual trends, better reproducing increasing trends driven by anthropogenic forcing and decadal variability modulated by natural climate variability. This data set is hence valuable for robust quantification of BCS-induced radiative forcing and attribution of snowmelt acceleration to snow darkening versus climate warming on a global scale.

The U.S. biodiesel industry faces significant economic challenges, exacerbated by declining glycerol coproduct values and rising feedstock costs and leading to numerous plant closures. In this study, we investigate the technoeconomic and environmental viability of electrochemically upcycling low-value industrial-grade crude glycerol (50 wt % glycerol) and methanol-depleted crude glycerol (80 wt % glycerol) into formic acid, a valuable chemical commodity. Through process modeling, we assess purification processes and electrochemical oxidation pathways for these waste glycerol streams. Our findings indicate that utilizing low-value crude glycerol can produce formic acid at competitive costs, contingent upon advancements in catalyst efficiency and reactor design. Life cycle assessments reveal that this approach could reduce environmental impacts compared to traditional formic acid production, especially as the U.S. electricity grid decarbonizes through additional renewable energy deployment. State-level analyses highlight the influence of regional electricity prices, water costs, policies, and incentives on economic feasibility. By enabling the circular use of biodiesel-derived waste, this work supports more resilient renewable fuel systems and advances sustainable chemical manufacturing.