Organosulfates (OSs) are key components of atmospheric secondary organic aerosols (SOAs), yet much of their ambient mass remains unexplained. This study demonstrates that dissolved SO2 reacts directly with major biogenic terpenoids (α-pinene, β-pinene, d-limonene, β-caryophyllene, and α-terpineol) in atmospheric condensed phases to form OSs without the need for traditional oxidants. Electrospray ionization mass spectrometry confirms product molecular formulas consistent with field measurements. Kinetic experiments reveal that α-pinene reacts with SO2 at a second-order rate constant of 4.0 ± 0.9 M-1 s-1 in a 50 vol % acetonitrile/water mixture, with the rate increasing nonlinearly as water content rises, reaching 12 ± 1 M-1 s-1 at 70 vol % water. pH-dependent experiments suggest that this reaction of α-pinene can occur at rates of 60-80 M-1 s-1 at pH 3-5, typical of cloud and aerosol water. This pathway could substantially contribute to OS formation and improve multiphase model predictions. Given that dissolved SO2 concentrations (∼10-3 M) far exceed those of OH, O3, or NO3 in aqueous phase, this pathway may rival or even surpass established oxidant-based sinks for terpenoids, contributing substantially to OS formation. Incorporating terpenoid + SO2 aqueous chemistry into multiphase models could thus enhance predictions of aerosol composition, particle acidity, and climate-relevant properties.

Eutrophic lakes, often enriched with various algae, can emit large amounts of volatile organic compounds into the atmosphere, which may serve as potential secondary organic aerosol (SOA) precursors. However, their contributions to SOA formation remain poorly understood. We herein conducted a real-time measurement of SOA formation from ambient air in the Taihu Lake-adjacent area in China during the summertime using an Oxidation Flow Reactor (OFR). The results showed that SOA formation in the OFR peaked at 2.62 ± 5.09 μg m-3 during daytime and 6.52 ± 8.02 μg m-3 during nighttime under equivalent photochemical ages of 2 and 3.3 days, respectively. Known precursors explained 23.8%-30.5% of the measured SOA, suggesting the importance of unidentified precursors in the Taihu Lake-adjacent area. Furthermore, by combining the positive matrix factorization and multilinear regression, we found that algal emissions contributed 17.7% and 6.4% to the potential SOA during daytime and nighttime. Heatwaves further enhanced the contribution of algal emissions to SOA, which can exceed 30% for temperatures over 35 °C. To the best of our knowledge, this is the first time that the contribution of algal emissions to SOA formation near a eutrophic lake was quantified. These findings highlight the critical role of algal emissions in SOA formation in adjacent areas of aquatic ecosystems.

Understanding the physicochemical processes that supply atmospheric aerosol iron (Fe) to the ocean is crucial for understanding of global biogeochemical cycles. Anthropogenic activity contributes significant fluxes of aerosol Fe to the atmosphere, the soluble fraction of which can modulate marine primary productivity upon its deposition to the ocean surface. However, anthropogenic aerosol Fe solubility remains poorly constrained, due in part to a lack of direct measurements spanning a multitude of anthropogenic sources. We measured solubility of aerosol Fe from several distinct anthropogenic combustion processes and fuel types. The median Fe solubility varied widely by source, ranging from 0.03 % for power plant coal fly ash to 55.87 % for biofuel burning; furthermore, residential coal burning aerosol possessed much higher Fe solubility than power plant coal fly ash. Using the new Fe solubilities reported herein, we updated parameters for anthropogenic aerosol Fe within the Community Earth System Model. Anthropogenic combustion is estimated to contribute up to 20 % of the global soluble Fe flux to the ocean in the present day. Furthermore, we identified residential coal burning as a previously neglected but potentially important source with regional flux contributions ranging from < 1 % to 21 %. Our work underscores the need to further refine understanding of aerosol Fe properties from a wide variety of anthropogenic sources by increasing observations in more novel aerosol regimes, with a focus on residential coal burning. This understanding will in turn aid in characterizing the influences of anthropogenic activity on past, present, and future atmospheric nutrient inputs to marine ecosystems.

This study aims to summarize the influence of air pollution on clouds and precipitation over the ocean and land. This paper summarizes global aerosol observation networks, including GAW and AERONET, as well as aerosol observation networks from various countries. Six typical regions, including North America, North Africa, South Africa, India, China, and the Indian Ocean, demonstrate aerosols’ seasonal and compositional variation patterns. This study also summarizes the impact of aerosols on the microphysical characteristics of stratiform clouds and precipitation mechanisms. The effect of aerosols on clouds varies across regions over land and ocean, and the impact of aerosols on the cloud water path differs significantly. Air pollution significantly affects precipitation by altering the microphysical properties of clouds, and this study is of great importance for understanding and predicting weather changes.

Heatwaves perturb plant physiology and monoterpene emissions, with important consequences for atmospheric chemistry and climate. Acyclic and cyclic monoterpenes differ markedly in their chemical reactivity, biosynthetic pathways, physiological functions, and atmospheric impacts, yet their heatwave responses remain poorly quantified, and current emission models generally assign them similar temperature sensitivities. Here, we combine leaf warming experiments, heatwave observations, and temperature-response modeling to show that acyclic monoterpenes from tropical trees in South China possess substantially higher temperature sensitivity than cyclic forms. As a result, heatwaves shift ambient mixture toward acyclic compounds, which approach half of measured monoterpenes and dominate calculated ozone and hydroxyl-radical reactivity. Default temperature algorithms in current emission models fail to reproduce this cyclic-to-acyclic shift, whereas the revised temperature functions developed here successfully capture the observed increase in acyclic fraction. Climate extremes may therefore alter atmospheric chemistry not only by changing monoterpene abundance, but also by reshaping monoterpene composition. Heatwaves reshape plant monoterpene emissions by preferentially increasing highly reactive acyclic isomers, altering atmospheric composition and increasing ozone and OH reactivity beyond changes in total monoterpene amounts

Nitrogen-containing organic compounds (NOCs), encompassing a complex suite of oxidized and reduced organic nitrogen species, exert significant impacts on atmospheric light absorption, oxidation capacity, and global nitrogen cycling. Despite the growing recognition of NOCs as key components of atmospheric organic matter, their formation through aqueous-phase processes and potential environmental impacts have long been underestimated. This review begins by summarizing the major classes of NOC molecules, then synthesizes observational evidence on their formation in the aqueous-phase, particularly highlighting its critical role in generating nitroaromatic and N-heterocyclic compounds. Built on the observational evidence, we further discuss the related evaluation of the multi-faceted environmental impacts arising from the aqueous-phase NOC formation. The evidence demonstrates that aqueous-phase NOC chemistry exerts significant influence on atmospheric compositions, contributes up to 90% of brown carbon's radiative effects, enhances oxidative capacity and secondary organic aerosol production, and influences nitrogen speciation in wet deposition. However, most current model assessments exhibit considerable limitations in quantifying these effects, stemming primarily from oversimplified parameterizations of aqueous-phase chemistry that fail to adequately represent the full complexity of atmospheric multiphase systems. Furthermore, existing observational data sets remain insufficient, severely constraining efforts to optimize model parameters and validate simulation outputs. To address these critical knowledge gaps, we propose an integrated research framework that combines long-term monitoring of key NOC and various precursors and advanced simulations of aqueous-phase chemistry at the micrometer-scale reaction environments, which would constrain the parameterization of future models for the aqueous-phase chemistry and impacts of NOCs.

The interaction between black carbon (BC) and polycyclic aromatic hydrocarbons (PAHs) is significant for their atmospheric evolution and impacts; however, the detailed mixing state of these substances from fresh emissions at the individual particle level is not well understood. In this study, the mixing of BC with PAHs from fresh emissions of typical biomass and coal burning was directly investigated using a single particle aerosol mass spectrometer (SPAMS), and the dependence on fuel types and burning conditions was also explored. PAHs are almost entirely (similar to 100%) associated with BC in both biomass and coal combustion. In BC-free particles, the number fraction of PAHs is approximately 80% and 60% for biomass and coal combustion, respectively. The distribution of PAH molecules is distinctly different for biomass and coal, with relatively higher molecular weight PAHs preferentially mixed with BC from biomass burning. Furthermore, the relative fraction of PAHs in BC particles decreases with increasing ignition temperature, indicating more complete combustion. The ignition temperature shifts the distinction of PAHs molecules associated with BC, with higher molecular weight PAHs being present under higher ignition temperatures. The variation in BC intensity can be well explained (R-2 = similar to 0.7-0.8) by a certain type of PAHs (>30% of the variance) and the ignition temperature in individual particles. These results reflect the different contributions of specific PAHs precursors to the formation of BC from biomass burning and coal combustion. These findings provide direct observational evidence of the influence of fuel type and ignition temperature on the mixing state of BC and PAHs in freshly emitted particles, which should be considered in models to better evaluate the evolution and impact of both BC and PAHs.

Peripheral subsidence of Northwest Pacific typhoons can trigger extreme surface ozone episodes, yet the relative contributions of local chemistry and vertical transport remain poorly constrained. Here we measured 30-min aerodynamic gradient fluxes of NOx, O-3, and CO at 118 and 168 m on Canton Tower (Pearl River Delta) during 2 September typhoons in 2021 and 2022. Surface O-3 climbed by >50% in both events. In September 2021, moderate subsidence created hot, stagnant conditions that accelerated local photochemical ozone production, yielding upward O-3 flux. In September 2022, stronger, long-lived subsidence instead injected ozone-rich air from aloft, causing downward O-3 flux despite favorable chemistry. This flux evidence demonstrates that subsidence intensity toggles the balance between local production and vertical transport of ozone, informing forecasts of coastal extreme-ozone risk.

Reactive uptake of methylglyoxal (Mgly) on aerosol particles is an important source of secondary organic aerosol (SOA), yet its significance remains highly uncertain due to the poorly constrained uptake coefficients (γMgly). Here, we quantified γMgly on deliquesced pH-buffered ammonium nitrate (AN) and sulfate/nitrate/ammonium (SNA) aerosols via flow tube experiments by directly measuring SOA formation under variable relative humidity (RH, 75-92%) and pH (3.1-4.4). For AN aerosols, γMgly ranged from 1.92 × 10-4 to 7.29 × 10-4, increasing with enhanced RH due to salting-out effects. Moreover, γMgly decreased by a factor of 2 to 10 as pH rose from 3.15 to 4.4 with NH3 addition, suggesting that acid-catalyzed reactions dominate the Mgly uptake. The pH dependence was captured by a first-order reaction rate constant (kI = 102.44-0.85·pH, R2 = 0.93). This kinetic parameter, together with effective Henry's law constants, can be implemented to update the γMgly parametrization. Addition of sulfate aerosols was found to strongly suppress γMgly, reducing kI to 12-38% of the estimation on AN-alone aerosols at a similar pH. Our findings underscore the critical role of aerosol pH and composition in Mgly uptake and provide kinetic parameters to atmospheric models to improve predictions of Mgly SOA.

To investigate optical properties, sources, and radiative effects of brown carbon (BrC), we conducted synchronous field campaigns in the Qinghai-Tibet Plateau (Yangbajing) and urban Guangzhou in July 2022, using multi-wavelength Aethalometer (AE33) and aerosol mass spectrometer (AMS) measurements. Total aerosol and BrC light absorption coefficients at 370 nm (Abs(total): 1.6 +/- 1.6 M m(-1); BrC: 0.2 +/- 0.3 M m(-1)) in Tibet were an order of magnitude lower than Guangzhou, attributed to extremely low aerosol/organic aerosol (OA) mass concentrations. However, BrC fractions in Abs(total) (15 % vs. 21 % at 370 nm) correlated with primary OA (POA) ratios, highlighting anthropogenic emission impacts even in this clean background. Diurnal variations (morning/evening peaks) of source-specific BrC absorption were regulated by local emissions (e.g., biomass burning, traffic emission) and regional secondary formation. Source apportionment revealed primary sources (biomass burning OA (BBOA), hydrocarbon-like OA (HOA)) dominated BrC absorption (> 75 %). The mass absorption cross-section (MAC) of HOA (2.08 m(2) g(-1) in Tibet; 2.57 m(2) g(-1) in Guangzhou) was comparable to that of BBOA (1.11-2.54 m(2) g(-1) in Tibet; 1.91 m(2) g(-1) in Guangzhou), indicating the high light absorption capacity of BrC from fossil fuel. Integrated "simple forcing efficiency" (370-660 nm) showed primary emissions contributed > 98 % of total radiative forcing at both sites. This study advances understanding of BrC dynamics and sources in diverse environments, underscores primary sources' critical role in BrC absorption, and emphasizes the need for source-specific OA optical parameterization.

Highly functionalized particle-phase organic nitrates (ONs) contribute substantially to secondary organic aerosol and influence NOx cycling through multiphase transformations. While photolysis of particle-phase inorganic nitrates is known to release nitrous acid to influence atmospheric oxidation, particle-phase ON photolysis remains poorly constrained. In this study, we determine suspended particle-phase photolysis rate constants for five synthetic multifunctional ONs and sulfur-substituted ONs (SONs) under dry conditions, using an oxidation flow reactor coupled to online aerosol measurements. The compounds include limonene- (LmSON, LmON), styrene- (SySON, SyON), and β-caryophyllene-derived (BcyON) species with additional carbonyl, sulfate, aromatic, or hydroxyl functionalities. We measure absorption cross-sections, infer quantum yields, and extrapolate to ambient solar conditions. The ambient particle-phase lifetimes range from 5.7 to 1.4 h, whereas no detectable photolysis for BcyON. Notably, carbonyl-nitrooxy conjugation enhances absorption at atmospherically relevant wavelengths and yields the fastest photolysis. We also observe net NOx production during photolysis, demonstrating its potential to influence NOx recycling. These results identify photolysis as an important sink for particle-phase ONs under dry conditions, with measurable effects on reactive nitrogen budgets. Given the functionalization typical of ambient ONs, particle-phase photolysis may be relatively rapid, highlighting the need to incorporate this pathway and its mechanistic controls into atmospheric models.

Amino acids, as important constituents of atmospheric organic nitrogen, play significant roles in global biogeochemical cycles. Their atmospheric fate has traditionally been attributed to photochemical processes, whereas the role of the unique chemistry in microdroplet, characterized by spontaneous OH radical generation, remains poorly understood. Here, we used a microdroplet generation apparatus coupled with online electrospray ionization mass spectrometry to study the spontaneous transformation of three representative amino acids (tryptophan, serine, and cysteine). By systematically varying reaction time, initial concentration and sheath gas pressure, we confirmed that these reactions occur specifically in microdroplets. Products analysis by a triple quadrupole mass spectrometer revealed spontaneously generated OH radicals as the primary driver, yielding distinct products such as hydroxylated monomers and dimers, that differs from that of bulk-phase oxidation. Quantitative assessment further revealed that high salinity, acidic pH, and oxidative atmospheres significantly accelerate the reactions, with notable compound-specific effects. High salinity most prominently enhanced serine transformation (∼7%), acidic condition (pH 3.0) maximally promoted tryptophan conversion (∼11%), and O2 primarily accelerated oxidation pathway of cysteine (∼17%). These findings reveal that the spontaneous transformation of amino acids in microdroplets, modulated by salinity, acidity, and oxygen availability, represents a previously unrecognized pathway for organic nitrogen conversion in the atmosphere. This work provides experimental evidence for integrating such processes into atmospheric chemistry models to reassess the cycling and lifetime of organic nitrogen.

Neonicotinoid insecticides (NNs) generate matrix-dependent photoproducts with significant atmospheric implications. Through high-resolution mass spectrometry analysis of five NNs (nitenpyram, thiamethoxam, imidacloprid, clothianidin, and dinotefuran), we demonstrate that solid-phase photolysis produces 2.5 times more gaseous products (430 vs 170 compounds) than liquid-phase reactions. Solid-state transformations yield concerning chlorinated VOCs (13% of products) and 59 light-absorbing brown carbon (BrC) species, while aqueous-phase reactions favor oxygenated CHO compounds (72-100% abundance). Mechanistic studies reveal that confined radicals in solids promote hazardous byproducts, including high-DBE (≥4) Cl-VOCs and BrC chromophores (DBE/C > 0.5). Volatility analysis shows that 85% of products are VOCs/IVOCs, but low-volatility BrC from solids may nucleate secondary aerosols. These findings identify NNs residues on crops and soils as previously overlooked emission sources for reactive compounds affecting air quality and the climate. Regulatory assessments must account for matrix-dependent photochemical pathways to fully evaluate NNs' environmental impacts.

Light-industrial biowastes are promising feedstocks for energy recovery via thermochemical conversion due to their high productivity and energy density. However, their heterogeneous and complex compositions obscure the underlying pyrolysis mechanisms, a pivotal conversion step, and compromise the fuel quality of the resulting products. To address this, the pyrolysis behaviors and kinetics of three representative biowastes, namely dark tea residue (DTR), brewer's grain residue (BGR), and oxytetracycline mycelia residue (OMR), were systematically investigated from raw to pretreated states using acid leaching and hydrothermal processing. These feedstocks exhibited a well-defined lignocellulose-protein compositional gradient, with a lignocellulose content decreasing from 69.57 to 1.22 wt% and protein content correspondingly increasing from 21.69 to 50.47 wt%, thereby establishing a rational framework for classifying and evaluating their thermochemical potential. Through combined iso-conversional (Friedman, FWO, KAS) and master-plots analyses, the average activation energies (DTR: 199.53 kJ mol-1; BGR: 184.06 kJ mol-1; OMR: 233.88 kJ mol-1) and reaction models (DTR: F3; BGR: F2; OMR: F4) were identified, highlighting the governing roles of protein and lignin in defining reaction order and energy barriers. Hydrothermal processing proved most effective for DTR, significantly enhancing pyrolysis efficiency, whereas acid leaching was superior for BGR and OMR, improving devolatilization and pyrolysis stability. Both pretreatments reduced emissions of greenhouse and nitrogen-containing gases and upgraded the fuel quality of the resulting pyrochars. Overall, this study advances the mechanistic understanding of pyrolysis across raw and pretreated light-industrial biowastes, providing theoretical insight and practical strategies for their identification and efficient thermochemical valorization.

The atmospheric aqueous phase represents a critical chemical reactor, where day-night alternation establishes distinct physicochemical regimes that transform the composition and impacts of organic aerosol. This study investigates how these contrasting regimes in cloud water govern the molecular characteristics of water-soluble organic matter (WSOM) and its subsequent health implications. Analysis of cloud water samples from Mt. Damaojian, southeastern China, revealed that nocturnal samples exhibited higher liquid water content, greater acidity, and a pronounced shift in chemical dominance from WSOM to secondary inorganic ions compared with daytime. Molecular analysis by Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) in both ESI ± modes identified CHO and CHON compounds dominated across both periods, but with a significant nocturnal enrichment of CHON species. The chemical signature of daytime WSOM exhibited a higher OSc and a proportion of Lipids reflecting dominant photo-oxidation processes. In contrast, nighttime samples showed higher N/C and a greater abundance of Protein1 (low oxidized protein), consistent with nitration and condensation reactions under dark conditions. Additionally, in vitro exposure experiments indicate that cloud-processed WSOM significantly inhibit cell viability, induce apoptosis, and trigger inflammation. Nighttime samples exhibited stronger cytotoxicity, likely due to their higher levels of nitrogen-containing and aromatic compounds. By integrating organic chemistry and toxicology, this work provides novel insights into the day-night dichotomy in cloud-processed WSOM composition and its corresponding biological impacts.

High-carbon aromatic hydrocarbons are under-characterized precursors of ozone and secondary organic aerosol (SOA) from solvent-intensive industries. We investigated aromatic emissions from 20 printed circuit board (PCB) manufacturing factories in the Pearl River Delta, China, using sorbent-tube samples collected from major production processes and exhaust outlets. Thermal desorption-gas chromatography/mass spectrometry was used to quantify 15 conventional C6–C9 volatile aromatic hydrocarbons (VAHs), 34 C10–C12 intermediate-volatility aromatic hydrocarbons (IAHs), and additional polycyclic aromatic hydrocarbons including naphthalene. Across process units, total aromatic concentrations ranged from 6.01 to 3,3924 μg/m3, and IAHs accounted for more than 71 % of measured aromatics, with IAHs/VAHs ratios of 3.37–7.30 across process units and a mean sample-wise ratio of 7.76 across 30 exhaust outlets. At the outlets, the ozone and SOA formation potentials of IAHs were on average 5.97 and 3.04 times the corresponding values of VAHs, respectively. Isodurene and ethyl-substituted xylene isomers dominated outlet concentration and ozone formation potentials, whereas naphthalene, toluene, and xylenes remained important for SOA formation potentials. These concentration- and profile-based results identify PCB manufacturing as a distinctive and under-characterized source of high-carbon aromatic precursors, and support including these species in industrial emission profiling, future emission-factor development, and control assessment.

Self-assembled monolayers (SAMs) have emerged as essential hole-selective contacts for high-performance inverted perovskite solar cells (PSCs). However, conventional flexible alkyl-chain linker inherently suffers from conformational fluctuations, leading to disordered molecular packing that exacerbates interfacial non-radiative recombination and open-circuit voltage (Voc) losses. Herein, we demonstrate that a regiochemistry-driven molecular assembly strategy effectively suppresses these voltage deficits. Phenylthiophene is introduced as a rigid linker, and the ortho-substituted isomer (CA2) exploits conformational locking to adopt a denser surface coverage compared to its meta counterpart (CA1). This highly ordered interfacial architecture eliminates energetic disorder and limits carrier trapping, effectively contributing to efficient interfacial charge transporting and facilitating high-quality perovskite growth. CA2-based inverted PSCs (1.57 eV) achieve a champion power conversion efficiency (PCE) approaching 26%, accompanied by an outstanding Voc of 1.203 V and a high fill factor (FF) of 85.47%. The voltage loss is calculated to be 0.381 V for CA1 and 0.367 V for CA2, and results indicate that trap-assisted recombination is mitigated in the CA2 device. Critically, a 15.136 cm2 mini-module achieves an efficiency of 23.70%, demonstrating excellent scalability. When extended to a 1.68 eV wide-bandgap perovskite, a certified efficiency of 22.21% is obtained, highlighting the potential of this molecular design for tandem applications. These results establish that coupling rigid linkers with regioisomer engineering minimizes interfacial losses for scalable perovskite photovoltaics.

Secondary organic aerosol (SOA) is a dominant constituent of fine particulate matter, exerting significant impacts on both climate and human health. Oxalic acid (C2), a key end-product formed from the oxidation of volatile organic compounds, can provide insights into the formation mechanism of SOA. Thus, long-term measurements of C2 and related compounds help understand the changes in SOA formation with decreasing pollutant levels. In this study, C2 and its homologs, along with five primary anthropogenic source markers and three SOA markers, were measured in the Pearl River Delta (PRD) during 2007-2018. The concentrations of C2 did not exhibit significant downward trends, despite substantial reductions in anthropogenic emissions, such as biomass burning (-11 %yr-1), vehicle emissions (-17 %yr-1), and cooking emissions (-7 %yr-1). Correlation analysis revealed that aerosol liquid water content (ALWC) and Ox (O3 + NO2) were the main drivers of C2 variations. Moreover, the relative contribution of biogenic SOA increased under cleaner conditions. A machine learning model was applied to quantify the impacts of changes in anthropogenic precursor emissions, biogenic precursor emissions, aqueous-phase oxidation processes, and gas-phase oxidation processes on C2 variability. As pollution levels declined, the impacts of gas-phase oxidation increased from 37 % to 55 %, whereas that of aqueous-phase oxidation declined from 42 % to 30 %. This shift indicated a transition from aqueous-phase to gas-phase pathways in C2 and SOA formation. Our findings highlight the increasing importance of gas-phase oxidation under low-pollution conditions and underscore the need for effective ozone control strategies to further reduce SOA in the future.