Abstract Nitrogen-containing microplastics (N-MPs) are widespread in soil and often exhibit distinct environmental behaviors and effects owing to their unique elemental composition and molecular structure. However, their toxicity to soil organisms remains poorly understood. To address this knowledge gap, the toxicity of pristine and aged polyamides (PA) was evaluated in earthworms (Eisenia fetida), a representative soil invertebrate. At 0.01% (w/w), aged PA increased the magnitude of body-weight loss, MDA levels, and AChE activity by 24.4%, 11.6%, and 24.1%, respectively, relative to pristine PA-MPs. Greater accumulation of aged PA-MPs was accompanied by enhanced oxidative damage and neurotoxicity. Integrated multiomics, quantitative real-time PCR, and biomarker analyses revealed that oxidative stress-mediated membrane damage promoted glutamate accumulation, receptor overactivation, Ca2+ overload, synaptic injury, and ultimately neurotoxicity. Pharmacological interventions and transmission electron microscopy of the ventral nerve cord provided functional and morphological support for this cascade. Radical quenching and comparative leachate bioassays further supported the important contribution of environmentally persistent free radicals in aged PA-MPs to neuronal damage. These findings define a mechanistic pathway for aged microplastic-induced neurotoxicity and provide a basis for assessing the ecological risks of aged N-MPs in soils.
Abstract The field of contaminated sediment remediation was disrupted two decades ago by the emergence of a new way to reduce risk in situ through the amendment of black carbon sorbents─activated carbon and specialized biochars. This required a paradigm shift from a focus on reducing pollutant mass to reducing exposure through bioavailability control. Sorbent amendment technology has advanced from laboratory and pilot field demonstrations to full-scale applications at many sites and has recently been incorporated in USEPA records of decision at Superfund sites. This perspective summarizes critical points in advancing the new technology: 1) accurate problem definition recognizing that sediment pollutant mass reduction does not necessarily lead to risk reduction, 2) breakthroughs in bioavailability science and unraveling the role of native black carbon in sediments, 3) demonstration of pollutant bioavailability reduction with strong sorption, 4) quantitative descriptions of the process, 5) addressing the challenges of mercury, 6) understanding unintended consequences, and 7) development of freely dissolved concentrations as a key bioavailability metric with regulatory and stakeholder engagement. The lessons learned in this journey from early science through technological maturity can help inform other technologies that are in development to address evolving threats to the environment.
Abstract Benzotriazole ultraviolet stabilizers (BUVs) are widespread emerging contaminants in soil. However, their transformation in the rhizosphere and the regulatory effects of plant oxidative stress on rhizosphere remediation remain unclear. The objective of this study was to investigate these effects using molecular simulations and rhizosphere and foliar exposure experiments. The removal efficiency of the four BUVs was 15–46% higher in the rhizosphere of Helianthus annuus than under natural soil degradation. The plant rhizosphere promoted BUV desorption from soil and induced hydroxylation as a specific transformation pathway. Direct rhizosphere exposure triggered oxidative stress and accelerated reactive oxygen species (ROS) accumulation in soil. Rhizosphere ROS contributed approximately 31.2%–42.7% to BUV transformation. Foliar exposure experiments suggested that plant oxidative stress is an important contributor to rhizosphere ROS generation. Under BUV stress, plant oxidative stress regulated the composition of dissolved organic matter (DOM) and the selective enrichment of bacteria, including Acidobacteriota, Actinomycota, and Bacteroidota. Multivariate correlation network analysis suggested that foliar exposure resulted in more complex interactions among rhizosphere microenvironmental characteristics than did direct rhizosphere exposure. This study provides insights into BUV transformation in the rhizosphere and establishes a framework for plant signal-guided rhizosphere remediation strategies.
Abstract Catechol is an important biomass-burning-derived phenolic compound and a precursor to secondary organic aerosols (SOAs). Although nitrate radicals (NO3) are recognized as major nighttime oxidants, the influence of the aerosol water content on heterogeneous NO3 oxidation of phenolic compounds remains poorly understood. Here, we investigate the impact of relative humidity (RH = 0–90%) on the heterogeneous oxidation of catechol thin films by nitrate radicals generated from the reaction of O3 and NO2. Product formation was characterized using Fourier transform infrared (FTIR) spectroscopy, UV–visible spectroscopy, electrospray ionization mass spectrometry (ESI-MS), ultrahigh-pressure liquid chromatography coupled with mass spectrometry (UHPLC–MS), and ion chromatography–mass spectrometry (IC–MS). Under dry conditions, oxidation favored nitration and oligomerization pathways, producing mono-, di-, and trinitrocatechols together with catechol dimers and trimers. These products exhibited enhanced absorption in the 300–500 nm region, characteristic of brown carbon chromophores. Increasing RH progressively suppressed the relative nitration capacity of the NO3/N2O5 system while promoting oxidative ring-opening reactions, leading to the formation of dicarboxylic acids, including cis,cis-muconic acid, 2,3-dihydroxymaleic acid, and oxalic acid. Product distributions revealed a transition from functionalization-dominated chemistry at low RH to fragmentation-dominated chemistry at high RH. These results indicate that RH strongly controls nighttime nitrate radical oxidation of biomass-burning phenolics by shifting product formation from light-absorbing nitroaromatic brown carbon toward highly oxygenated fragmentation products. The findings provide new mechanistic insights into the role of aerosol water in governing the chemical aging and optical evolution of biomass-burning aerosols.
Abstract Electrification and lightweighting are reshaping vehicle designs and materials demand, with uncertain net effects on life cycle greenhouse gas (GHG) emissions. Most existing fleet studies treat material choices, materials markets, and vehicle adoption separately, without capturing feedbacks between design, supply chains, and consumer behavior. This study develops an integrated system dynamics–life cycle assessment (SD–LCA) framework to explore these interactions for the U.S. light-duty vehicle fleet from 2000 to 2060. The model extends an established powertrain diffusion framework by endogenizing vehicle body material selection, battery capacity evolution, and materials market responses, linking these dynamics to a bottom-up life cycle assessment of fleet GHG emissions. Scenario analysis shows that increasing aluminum use in lightweight gasoline vehicles improves their utility and market share, largely offsetting use-phase GHG savings and yielding only modest reductions in total fleet emissions. In contrast, faster battery electric vehicle adoption raises cradle-to-gate emissions but more than compensates through lower use-phase emissions, reducing total fleet GHGs. Shifts in vehicle material demand also generate transient imbalances in steel and aluminum markets, temporarily lowering recycled fraction and increasing cradle-to-gate emissions. The SD–LCA framework demonstrates how feedbacks between vehicle design, materials supply, and consumer adoption shape fleet decarbonization pathways.
