Polycyclic aromatic compounds (PACs) are organic pollutants associated with incomplete combustion processes and connected to severe health effects. Their connection to micro-nanoplastics (MNPs) emitted as particulate matter from incineration of plastics remains poorly explored. In this study, we detected 65 Polycyclic Aromatic Hydrocarbon (PAH), oxygenated (OPAH) and nitrated (NPAH) PAC species in MNPs emitted during the incineration of three widely used plastic materials, high-density polyethylene (HDPE), polypropylene (PP) and polyvinyl chloride (PVC). MNPs were generated using the incineration exposure generation system (INEXS) and their PAC profile was offline analyzed using gas chromatography-mass spectrometry. Notably, one of the most abundant species in all three plastics was Benzanthrone, an OPAH previously associated with traffic and biomass burning emissions. MNPs emitted by PVC incineration contained emerging highly toxic PAC species such as benzo(c)fluorene, dibenzopyrenes, and 6-nitrochrysene. Our findings highlight the importance of monitoring beyond the legacy 16 EPA members which accounted only by 12%, 47%, and 41% of the associated carcinogenic potency (expressed as BaPeq), for PVC, PP and HDPE respectively. These results raise concerns for potential health implications and underscore the urgent need for further research on this new environmental challenge, MNP pollution and its association with toxic persistent pollutants.

Although citrus processing wastewater is rich in bioactive compounds and nutrients, the significant potential of the specific feedstock for valorization still remains largely unexploited. Thus, a citrus processing wastewater-based biorefinery was employed to recover carotenoids and polyphenols, while producing microbially derived bacterial cellulose nanocrystals. The solid fraction of the effluent was applied in solid-liquid extraction using various green- and petrochemical-based solvents, yielding 1.97 ± 0.03 mg of carotenoids per g of dry solid via a mixture of D-limonene/ethanol/acetic acid. A continuous adsorption/desorption system was developed, adsorbing 89.1 ± 0.63% (w/v) of the initial phenolic content. Different solvents were assessed as elution agents maximizing the desorption of the phenolic content (76 ± 7.25%, w/v) using 75% ethanol. The remaining sugar-rich liquid was subsequently utilized for bacterial cellulose manufacture employing Komagataeibacter sucrofermentans DSM 15973. Elevated fermentative production was achieved at pH-value 6.0 using a surface-to-volume ratio of 1.53 cm⁻¹, yielding 4.98 ± 0.28 g L⁻¹ of the biopolymer following 6 d of incubation. The bacterial cellulose formed was processed using sulfuric acid, aiming to hydrolyze the amorphous fraction and produce a biomaterial of higher crystallinity as well as enhanced stability and mechanical properties as compared to the pristine biopolymer. The nanocrystals produced exhibited colloidal stability (−24.73 ± 1.11 mV), enhanced crystallinity (85.2%) and reduced thermal stability (297.1 °C) as compared to bacterial cellulose. The study demonstrated a sustainable biorefinery approach for efficient valorization of citrus processing wastewater towards production of industrially important bioactive compounds and biopolymers.

Wildfire particulate matter from Canadian forest fires significantly impacted the air quality in the northeastern United States during the summer of 2023. Here, we used real-time and time-integrated instrumentation to characterize the physicochemical properties and radiative effects of wildfire particulate matter reaching the metropolitan areas of New Jersey/ New York during this extreme incident. The radiative forcing of −352.4 W/m² derived here based on the measured optical properties of wildfire particulate matter explains, to some extent, the ground level temperature reduction of about 3 °C observed in New Jersey/ New York City during this incident. Such negative radiative forcing in densely populated megacities may limit natural ventilation, increase the residence time of wildfire particulate matter and background air pollutants, exacerbating public health risks. This study highlights the importance of radiative effects from wildfire particulate matter in densely populated areas and their potential implications for climate, air quality and public health.

Here, the light absorption of brown carbon (BrC) emitted by wood combustion and denuded from volatile organic carbon (VOC) at 300 °C is elucidated using a recently developed thermal decomposition platform coupled with a suite of real-time aerosol instrumentation and time-integrated sampling systems. The BrC particle size distribution, morphology and optical properties are closely controlled by increasing the combusted wood mass from 50 to 600 mg to emulate those measured for “real world” wildfire particulate matter (PM) emissions. Size-fractionation of such wildfire-like BrC reveals that the PM_0.1–2.5 fraction contains high molecular weight, carcinogenic polycyclic aromatic hydrocarbons (PAHs) and absorbs up to five times more light compared to the PM_0.1 fraction. Thus, increasing the combusted wood mass from 50 to 600 mg increases the PM_0.1–2.5 concentration by a factor of about eight and enhances the overall BrC mass absorption cross-section, MAC, up to a factor of two at a wavelength of 405 nm. Condensation of VOC on BrC reduces its MAC up to 40 %. Still, the particle size seems to largely determine the BrC light absorption, as large VOC-rich particles absorb more light compared to small VOC-lean ones. The size-resolved BrC MAC measured here can be interfaced with climate models to estimate the climate impact of wildfire PM emissions.