Characterizing the photodegradation-induced release of volatile organic compounds from bottled water containers.

While plastic water bottles are known to potentially release various volatile organic compounds (VOCs) when exposed to light, existing knowledge in this field remains limited. In this study, we systematically examined the composition, yield, and toxicity of VOCs released from six plastic containers obtained from different continents under UV-A and solar irradiation. After light exposure, all containers released VOCs, including alkanes, alkenes, alcohols, aldehydes, carboxylic acids, aromatics, etc. The 1#, 3#, 4#, 5#, and 6# containers exhibited 35, 32, 19, 24 and 37 species of VOCs, respectively. Specifically, the 2# container released 28 and 32 series of VOCs after 1-day (short-term) and 7-day (long-term) UV-A irradiation, respectively, compared to 30 and 32 species under solar irradiation. Over half of the VOCs identified were oxidized compounds alongside various short-chain hydrocarbons. Significant differences in VOC compositions among the containers were observed, potentially originating from light-induced aging and degradation of the polyethylene terephthalate structure in the containers. Toxicological predictions unveiled distinctive toxic characteristics of VOCs from each container. For example, among the various VOCs produced by the 2# container, straight-chain alkanes like n-hexadecane (544-76-3) were identified as the most toxic compounds. After long-term irradiation, the yield of these toxic VOCs from the 2# container ranged from 0.11 ng/g to 0.79 ng/g. Considering the small mass of a single bottle, the volatilization of VOCs from an individual container would be insignificant. Even after prolonged exposure to light, the potential health risks associated with inhaling VOCs when opening and drinking bottled water appear manageable.

Microplastics and volatile organic compounds released from face masks after disinfection: Layers and materials differences.

Effective disinfection methods are critical for ensuring the reusability of masks, yet these methods may inadvertently introduce health concerns associated with microplastics (MPs) and volatile organic compounds (VOCs). This study investigated the impact of ultraviolet germicidal irradiation (UVGI) and sodium hypochlorite (NaClO) bleaching on mask filter layers composed of four distinct materials. Our results revealed that UVGI induced more pronounced damage compared to bleaching, leading to the significant release of both MPs and VOCs. After UVGI treatment at conventional disinfection doses, meltblown (MB) fabrics released MPs reaching 864 ± 182 µg/g (92 ± 19 particles/g). For all filter layers, the quantity of released MPs followed the order: MB > HDPE>PU ≈ NW. These MPs were identified as degraded debris from the mask filter layers. The specific VOCs generated varied depending on the material composition. Non-woven (NW) and MB fabrics, both comprised of polypropylene, predominantly produced various branched aliphatic hydrocarbons and their derivative oxides. The cotton-like fabric, composed of high-density polyethylene, primarily emitted different linear aliphatic hydrocarbons and oxygenates. In contrast, the polyurethane filter layer of reusable masks released aromatic compounds, nitrogenous compounds, and their oxidation products. The formation of VOCs was primarily attributed to bond breakage and oxidative damage to the filter structure resulting from the disinfection process. In summary, as UVGI induced higher yields of MPs and VOCs compared to bleaching, the latter would be a safer option for mask disinfection.

Interfacial quantum chemical characterization of aromatic organic matter adsorption on oxidized microplastic surfaces.

Examining the adsorption efficiency of individual contaminants on microplastics (MPs) is resource-intensive and time-consuming. To address this challenge, combined laboratory adsorption experiments with model simulations were performed to investigate the adsorption capacities and mechanisms of MPs before and after aging. Our adsorption experiments revealed that aged polyethylene (PE) and polyvinyl chloride (PVC) MPs exhibited increased adsorption capacity for benzene, phenol, and naphthalene. Additionally, density functional theory (DFT) simulations provided insights into changes in adsorption sites, adsorption energy, and charge density on MPs. The π bond of the benzene ring emerged as a pivotal factor in the adsorption process, with van der Waals forces exerting dominant influence. For instance, the adsorption energy of benzene on pristine PE was -0.01879 eV. When oxidized groups, such as hydroxyl, carbonyl, and carboxyl, on the surface of aged PE became the adsorption sites, the adsorption energy increased to -0.06976, -0.04781, and -0.04903 eV, respectively. Regions with unoxidized functional groups also exhibited higher adsorption energies than pristine PE. These results indicated that aged PE had a stronger affinity for benzene compared to pristine PE, enhancing its adsorption. Charge density difference and energy density of states corroborated this observation, revealing larger π-bond charge accumulation areas for benzene on aged PE, suggesting stronger dipole interactions and enhanced adsorption. Similar trends were observed for phenol and naphthalene. In summary, the DFT calculations aligned with the adsorption experiment findings, confirming the effectiveness of simulation methods in predicting changes in the adsorption performance of aged MPs.

Gaseous products generated from polyethylene and polyethylene terephthalate during ultraviolet irradiation: Mechanism, pathway and toxicological analyses.

The generation of various degradation products from microplastics (MPs) has been confirmed under ultraviolet (UV) irradiation. The gaseous products, primarily volatile organic compounds (VOCs), are usually overlooked, leading to potential unknown risks to humans and the environment. In this study, the generation of VOCs from polyethylene (PE) and polyethylene terephthalate (PET) under UV-A (365 nm) and UV-C (254 nm) irradiation in water matrixes were compared. More than 50 different VOCs were identified. For PE, UV-A-derived VOCs mainly included alkenes and alkanes. On this basis, UV-C-derived VOCs included various oxygen-containing organics, such as alcohols, aldehydes, ketones, carboxylic acid and even lactones. For PET, both UV-A and UV-C irradiation induced the generation of alkenes, alkanes, esters, phenols, etc., and the differences between these two reactions were insignificant. Toxicological prioritization prediction revealed that these VOCs have diverse toxicological profiles. The VOCs with the highest potential toxicity were dimethyl phthalate (CAS: 131-11-3) from PE and 4-acetylbenzoate (3609-53-8) from PET. Furthermore, some alkane and alcohol products also presented high potential toxicity. The quantitative results indicated that the yield of these toxic VOCs from PE could reach 102 µg g-1 under UV-C treatment. The degradation mechanisms of MPs included direct scission by UV irradiation and indirect oxidation induced by diverse activated radicals. The former mechanism was dominant in UV-A degradation, while UV-C included both mechanisms. Both mechanisms contributed to the generation of VOCs. Generally, MPs-derived VOCs can be released from water to the air after UV irradiation, posing a potential risk to ecosystems and human beings, especially for UV-C disinfection indoors in water treatments.

Modifications of microplastics in urban environmental management systems: A review.

Microplastics (MPs) are a worldwide environmental pollution issue. Besides the natural environmental stresses, various treatments in urban environmental management systems induce modifications on MPs, further affecting their environmental behavior. Investigating these modifications and inherent mechanisms is crucial for assessing the environmental impact and risk of MPs. In this review, up-to-date knowledge regarding the modifications of MPs in urban environmental management systems was summarized. Variations of morphology, chemical composition, hydrophilicity and specific surface area of MPs were generalized. The aging and degradation of MPs during drinking water treatment, wastewater treatment, sewage sludge treatment and solid waste treatment were investigated. A high abundance of MPs occurred in sewage sludge and aging solid waste, while digestion and composting contributed to significant decomposition and reduction of MPs. These treatments have become converters for MPs before entering the environment. Several novel technologies for MPs removal were listed; However, no appropriate methods can be put into actual application by now, except the membrane separation. The corresponding effects of degradation on the behaviors of MPs, including adsorption, sinking and contaminant leakage, were discussed. Finally, three priorities for research were proposed. This critical review provides viewpoints and references for risk evaluation of MPs after treatments in urban environmental management systems.

Gut Microbial Profiles in Nereis succinea and Their Contribution to the Degradation of Organic Pollutants.

Gut microbiota of wildlife are usually exposed to and involved in degrading environmental pollutants, yet their biodegrading capacity remains largely unexplored. Here, we analyzed gut microbial profiles of a marine benthic polychaete, Nereis succinea, and elaborated the capacity of gut microbiota in degrading various organic pollutants, including polycyclic aromatic hydrocarbons, pesticides, phenols, and synthetic musks. High-throughput sequencing analysis revealed that the structures of microbial communities, including bacteria, fungi, and archaea, varied along the gut, manifesting distinct structural features in the fore-, mid-, and hindgut regions. Community-level physiological profiles and the capacity of gut microbiota in degrading the pollutants showed profound gut region and oxygen dependent features. In general, anaerobes were more active in degrading the pollutants, and those in the midgut presented the maximum degrading potential. Degradation capability of the gut microbiota was further quantitatively validated in an in vitro culture system using chlorpyrifos and malathion as representative compounds. Our results demonstrated a potential impact of gut microbiota in wildlife on the fate of organic pollutants in the ecosystem, which calls for further research on the influences of gut microbiota on biotransformation and bioaccumulation of xenobiotics in organisms.