Environmental Science & Technology Letters Environ.最新文献

Residential solid fuel combustion is a major source of atmospheric brown carbon (BrC), yet the emission characteristics remain poorly constrained, leading to substantial uncertainties in estimating climatic impacts. In this study, the liquid chromatography–photodiode array–high-resolution mass spectrometry (HPLC–PDA–HRMS) method was applied to resolve the molecular fingerprints of BrC emitted from biomass burning and coal combustion. The mass absorption efficiency (MAE) of biomass-derived BrC was consistently higher than that of coal-derived BrC over the range of 300–500 nm, reflecting distinct source-dependent chromophoric compositions. A total of 29 chromophores (3.3–4.2 g kg^–1) identified in biomass burning explained 35.4–50.3% of the total BrC light absorption, while 20 chromophores (0.4 g kg^–1) from coal combustion accounted for 37.0%. Biomass-derived BrC was dominated by lignin pyrolysis products, stilbenes, coumarins, and flavonoids, while coal-derived BrC contained more polycyclic aromatic hydrocarbons and N/O-containing aromatics. Nitrophenols, such as methoxy nitrocatechol and 4-nitro-3-vinylsyringol, were detected in flaming emissions but absent in smoldering, serving as distinct molecular tracers for combustion conditions of biomass burning. These results establish source-resolved chromophoric profiles and reveal distinct optical contributions of biomass- and coal-derived BrC, providing molecular-level insights to improve atmospheric BrC source apportionment and radiative forcing assessment.

Colorimetric measurements of inorganic fluoride (F^–) offer a rapid screening of biodefluorination, but existing methods fall short when they are applied to growing cultures. By systematically replacing mineral salt medium components, we demonstrate that a modified HEPES/Cl^–-rich medium allows colorimetric F^– quantification (20–200 μM) during biodefluorination of 1-fluorodecane (FD), 4,5,5-trifluoropent-4-enoic acid (TFEA), and 4,4,4-trifluoro-3-(trifluoromethyl) crotonic acid (SFCA). Applied in a deep 96-well microtiter plate format, this approach explored the biodefluorination of these compounds in growing axenic cultures, resting cell incubations, and mixed environmental cultures. Sphingopyxis sp. strain NJF-3 and Rhodococcus sp. strain NJF-7 exhibited differential defluorination of TFEA and SFCA. Resting cells exhibited limited defluorination activity to TFEA and SFCA, but strain NJF-7 displayed higher TFEA defluorination (219 μM F^–) than strain NJF-3 (39.1 μM F^–), indicating a greater growth-independent defluorination capacity. Defluorination by environmentally sourced microbial communities varied, potentially reflecting differences in sample origin (water vs soil). Correlation analysis of intermediates measured in different SFCA-defluorinating cultures indicated that abiotic and biotic reactions contribute to SFCA transformation, with a β-oxidation-type pathway inferred for the biotransformation. The refined approach expands the tool box for investigating biodefluorination in microbial enrichment and pure culture studies.

Efficient electrochemical conversion of wastewater nitrate to sustainable ammonia requires comprehensive mechanistic understanding and stringent control over competing pathways among multiple aqueous nitrogen intermediates─a challenge that underscores the need for in situ and operando surface analyses of electrocatalysts. In this study, we describe scanning electrochemical microscopy (SECM)-based approaches to characterize the nitrate reduction reaction (NO₃RR) on Ti and Cu. These methods facilitate the assessment of catalytic activity, product selectivity, and surface-adsorbed intermediates. By combining tailored chronoamperometric protocols, we achieved operando visualization of NO₃RR onset potentials (−0.35 V vs RHE for Ti and −0.16 V vs RHE for Cu) and verified potential-dependent nitrogen product distributions through stepwise quantification of ammonia, hydroxylamine, and nitrite. Furthermore, in situ surface interrogation SECM directly titrates surface-adsorbed H* and O*, revealing their coverage shifts under varying potentials and reaction times during the NO₃RR and providing evidence for a hydrogen-mediated pathway on Ti. The methodology establishes a robust SECM-based platform for systematically benchmarking electrocatalyst performance and is readily applicable to the NO₃RR on other catalysts and even other reactions that produce a complex array of intermediates.

Solid fuel combustion is an important source of nitrogen-containing brown carbon (BrC) and secondary aerosol precursors. However, knowledge of the emission of imidazoles (IMs) in nitrogen-containing BrC and their transformation remains limited. This study investigated the emissions of IMs from 11 solid fuel combustions and subsequent photochemical evolution. The reaction pathways and light absorption of IMs were estimated through quantum chemical calculations. The potential toxicity of IMs for aging products was predicted with machine learning. The results showed that emission factors (EFs) of IMs were higher from biomass burning (BB) than from coal combustion (CC). Maize stalks exhibited the highest ∑IMs EFs, while anthracite coal showed the lowest ones. Alkyl IMs (Alk-IMs) and benzene-ring IMs (Bn-IMs) dominated the ∑IMs in BB (85%) and CC (52%). During aging, Alk-IMs underwent •OH substitution reactions, forming poorly oxygenated hydroxyimidazole derivatives (O/N = 0.5). Conversely, based on density functional theory calculations, •OH oxidation of Bn-IMs and carboxyl IMs occurred more easily, forming highly oxygenated imidazole derivatives (O/N = 1–2) with carboxyl groups. The light absorption of these highly oxygenated derivatives decreased by 17–28%, while their health risk probability increased by 1.12–2.27 times compared to those of their precursors. These findings improved our understanding of the residence time and interaction with other pollutants of IMs.

Wet scavenging is the major sink for black carbon (BC), while the responses of BC emitted from different sources remain poorly quantified. In this study, the below-cloud scavenging of BC from biomass burning (BC_bb) and fossil fuel combustion (BC_ff) was investigated, using year-round in situ measurements in Nanjing, China. A statistical approach was developed to quantify the source-specific mass absorption efficiency (MAE). Results showed that BC_ff was less susceptible to scavenging than BC_bb, with wet scavenging ratios of 0.13 and 0.45, respectively. Additionally, BC_ff exhibited a stronger light-absorbing ability than BC_bb, with MAE values of 8.0–12.0 and 3.4–8.0 m² g^–1 (25–75th percentiles), respectively. Consequently, the MAE of BC increased significantly with precipitation amount, driven by a combination of a rising BC_ff proportion, a higher intrinsic MAE of BC_ff, and enhancement of the MAE for both BC types due to high humidity. Neglecting the source-specific MAE could lead to substantial biases in the estimated direct radiative forcing, which can exceed 20% in regions with high BC_bb contributions. This study strongly suggests that BC_ff and BC_bb should be treated separately in models to improve the simulation of atmospheric loadings and climate impacts.

Rising demand for lithium (Li) driven by lithium-ion battery (LIB) proliferation underscores the importance of sustainable recycling. Conventional processes for recovering Li from spent LIB leachate are energy-intensive or chemically demanding, compromising the environmental and economic viability. This study introduces an ecofriendly approach using capillary-driven three-dimensional (3D) evaporative crystallization within a porous cotton matrix. Low-solubility salts (CoCl₂, MnCl₂, and NiCl₂) crystallize proximally, while highly dissolvable LiCl migrates toward the distal zone, achieving spatial separation on the crystallizer. Maximum selectivity reached 109.5 (Li/Co), 7.8 (Li/Ni), and 3.2 (Li/Mn) in the simulated leachate, corresponding to a 4.7-fold enrichment of Li abundance. A comparable selective Li separation was demonstrated for a real leachate, confirming the practical potential of the approach. The natural-physiochemical-process-induced 3D evaporative crystallization eliminates high energy or chemical inputs, providing a sustainable and low-cost pathway for selective Li recovery from variable spent LIB leachates.

We quantify volatile organic compound (VOC) emissions from indoor surface swabs and portable air cleaner (PAC) filters collected in a home 30 days after the 2025 Los Angeles wildland-urban interface (WUI) fires. We calculate emissions for 17 fire-relevant compounds. Surface emissions exceeded those of clean controls, and emissions from a windowsill in a room without a PAC were ∼15× and ∼2× higher for benzene and toluene, respectively, than rates reported in the literature for comparable materials unaffected by smoke/soot. Particle filters installed in PACs at the start of the fire emitted aromatics at rates comparable to those reported in a study where filters operated for 200 days in a city. Emissions from activated carbon filters exceeded those of the particle filters tested as part of the present study by >3×. A windowsill in a room without a PAC off-gassed more VOC mass than a windowsill in a room with a PAC, suggesting that air cleaners can reduce surface contamination. Modeling with benzene emission rates from impacted surfaces in a hypothetical indoor space resulted in a predicted indoor concentration ∼6× greater than outdoors. This study shows surfaces act as persistent VOC sources following WUI fires and indicates indoor surfaces affect exposure during and after fire events.