Microplastics (MPs) pollution has become a global environmental concern. MPs alone and in combination with pollutants can potentially cause significant harm to organisms and human beings. Weathering of MPs under various environmental stresses increases the uncertainty of their environmental fates. Compared with field surveys, laboratory simulation experiments are appropriate to simplify the research procedures and investigate the mechanisms. In this review, the effects of abrasion, solar radiation, chemical and thermal oxidation, microbial adhesion and colonization, and other environmental factors on the MPs and the relative laboratory simulation methods were summarized and discussed. Photo-oxidation and abrasion are the most appliable methods due to easy operation and adjustable weathering degree. Furthermore, the structural and components changes in weathering process and the applied characterization methods were generalized. In addition, one of important environmental behaviors, adsorption of the weathered MPs towards two typical pollutants was analyzed. Finally, three priorities for research were proposed. This paper conducts systematic summarized of the MPs weathering process and provides a reference for future studies to accurately determine the environmental risks of weathering MPs.

Microplastic (MP) pollution and its potential to concentrate and transport organic contaminants in environments have recently gained widespread attention. Compared to traditional nonpolar plastics such as polypropylene (PP) and polyethylene (PE), study about the environmental behavior of polyurethane (PT), polyuria (PU) and urea-formaldehyde resin (UF), which are typically used as shell materials for pesticide microcapsules and have polar structure is scarce. In the present study, we investigated the sorption capacities and binding mechanisms of PT, PU and UF for three polycyclic aromatic hydrocarbons (PAHs, naphthalene, phenanthrene (PHE), and pyrene) and two PHE derivates (ethylphenanthrene-2-carboxylate (2-CPHE) and 2-methylphenathrene (2-MPHE)) selected as the model compounds, and the effects of salinity and UV and/or H₂O₂ aging treatments on PHE sorption to MPs. The results showed that PT, PU and UF had negative surface charges, micron-scaled sizes and abundant polar functional groups containing O and N elements. PT, PU and UF could sorb PAHs efficiently with sorption coefficients (Kd) being in the range of 8.11 × 10³–9.53 × 10⁵ (L/Kg) and partitioning was the main sorption mechanism with polar interactions (H-boning and p/π-π EDA interactions) also contributing. The sorption capacity of the three MPs changed mainly depending on their glass transition temperatures (Tg). Furthermore, high salinity decreased the surface zeta-potential of the MPs and enhanced PHE sorption to MPs. In addition, aging treatments with UV and/or H₂O₂ markedly decreased the Tg of PT and enhanced its sorption capacity for PHE, while opposite results were obtained for PU. The findings on the sorption mechanisms of PAHs to agricultural MPs are useful for predicting the transport, fate and persistence of the co-existing HOCs in agricultural ecosystems and provide a scientific basis for the comprehensive risk assessment of agricultural MPs.

Global burden of disease estimates reveal that people in Nigeria are living shorter lifespan than the regional or global average life expectancy. Ambient air pollution is a top risk factor responsible for the reduced longevity. But, the magnitude of the loss or the gains in longevity accruing from the pollution reductions, which are capable of driving mitigation interventions in Nigeria, remain unknown. Thus, we estimate the loss, and the gains in longevity resulting from ambient PM2.5 pollution reductions at the local sub-national level using life table approach. Surface average PM2.5 concentration datasets covering Nigeria with spatial resolution of ∼1 km were obtained from the global gridded concentration fields, and combined with ∼1 km gridded population of the world (GPWv4), and global administrative unit layers (GAUL) for territorial boundaries classification. We estimate the loss or gains in longevity using population-weighted average pollution level and baseline mortality data for cardiopulmonary disease and lung cancer in adults ≥25 years and for respiratory infection in children under 5. As at 2015, there are six “highly polluted”, thirty “polluted” and one “moderately polluted” States in Nigeria. People residing in these States lose ∼3.8–4.0, 3.0–3.6 and 2.7 years of life expectancy, respectively, due to the pollution exposure. But, assuming interventions achieve global air quality guideline of 10 μg/m3, longevity would increase by 2.6–2.9, 1.9–2.5 and 1.6 years for people in the State-categories, respectively. The longevity gains are indeed high, but to achieve them, mitigation interventions should target emission sources having the highest population exposures.

The aim of this study was to determine the effect of biochar aging on the content of polycyclic aromatic hydrocarbons (PAHs) (the total content – Ctot, and the freely dissolved – Cfree) in biochar and its ecotoxicity. Two biochars (BCS and BCM) with varying properties were aged for 420 days at different temperatures (−20 °C, 4 °C, 20 °C, 70 °C), at a variable temperature (−20/20 °C), in the presence of nutrients, and in the presence of inoculum and nutrients. After the aging process, Ctot and Cfree PAHs were determined in samples obtained and an ecotoxicological analysis was performed, which involved tests with bacteria (Vibrio fischeri), invertebrates (Folsomia candida) and plants (Lepidium sativum). Aging significantly affected all the parameters tested. The range of changes in the studied parameters depended on the type of biochar and ageing conditions. In the case of most of the aging methods, PAH content (Ctot, Cfree) and toxicity were found to decrease. Aging in the presence of microorganisms and nutrients and in the presence of nutrients alone caused the greatest reduction in Ctot PAH content (a reduction from 30 to 100% relative to non-aged biochar), Cfree PAH content (a reduction from 12 to 100%), root growth inhibition (a reduction from 73 to 90%), and luminescence inhibition (a reduction from 24 to 100%). In the case of Cfree PAHs and toxicity to F. candida, some aging methods caused their increase. The study also found a significant relationship between the changes in Ctot PAH content during aging and inhibition of root growth (BCS, BCM) and inhibition of V. fischerii luminescence (BCM). In no case was a significant correlation (P ≥ 0.05) between Cfree PAHs and the investigated toxicity parameters found.

The increasing application of iron-based nanoparticles (NPs), especially high concentrations of zero-valent iron nanoparticles (nZVI), has raised concerns regarding their environmental behavior and potential ecological effects. In the environment, iron-based NPs undergo physical, chemical, and/or biological transformations as influenced by environmental factors such as pH, ions, dissolved oxygen, natural organic matter (NOM), and biotas. This review presents recent research advances on environmental transformations of iron-based NPs, and articulates their relationships with the observed toxicities. The type and extent of physical, chemical, and biological transformations, including aggregation, oxidation, and bio-reduction, depend on the properties of NPs and the receiving environment. Toxicities of iron-based NPs to bacteria, algae, fish, and plants are increasingly observed, which are evaluated with a particular focus on the underlying mechanisms. The toxicity of iron-based NPs is a function of their properties, tolerance of test organisms, and environmental conditions. Oxidative stress induced by reactive oxygen species is considered as the primary toxic mechanism of iron-based NPs. Factors influencing the toxicity of iron-based NPs are addressed and environmental transformations play a significant role, for example, surface oxidation or coating by NOM generally lowers the toxicity of nZVI. Research gaps and future directions are suggested with an aim to boost concerted research efforts on environmental transformations and toxicity of iron-based NPs, e.g., toxicity studies of transformed NPs in field, expansion of toxicity endpoints, and roles of laden contaminants and surface coating. This review will enhance our understanding of potential risks of iron-based NPs and proper uses of environmentally benign NPs.

Earthworm density and feeding during exposure to contaminated soil have been used inconsistently in bioaccumulation studies, which may lead to possible errors in risk assessment and modeling. Hydrophobic organic pollutants with a wide range of environmental properties (phenanthrene, pyrene, lindane, p,p′-DDT, and PCB 153) were used to study the effect of different earthworm densities in combination with the presence or absence of feeding on bioaccumulation factors (BAFs). Similar BAFs were found at various soil-to-worm ratios, with the exception of phenanthrene. We recommend using at least 15 gsoil dw per earthworm. The absence of feeding doubled the BAFs and, thus, using no food ration can be considered as “the worst case scenario”. Whenever food is to be applied (i.e. to ensure the validity of the test in earthworm mass loss), we suggest feeding depending on the organic carbon content of the studied soil.

Mass transfer processes of pollutants from non-aqueous phase liquids (NAPL) may control groundwater pollution at abandoned industrial sites. We studied release kinetics of polycyclic aromatic hydrocarbons (PAHs) from fresh and aged tar phases using a dialysis tubing technique. Time for equilibration ranged from several days to more than three years. For fresh tar materials the release seems to be limited by retarded pore diffusion, while for two of three aged tars diffusion limited release influenced by dissolved organic matter (DOM) was assumed. The equilibration process was driven by solubilization thermodynamics expressed by Raoult's law. Yet, solubility enhancement was observed potentially due to the presence of organic mobile sorbents. The results show that the release of PAHs from tar phases is generally rate limited and partitioning according to Raoult's law is the driving mechanism of the exchanges process.

To date, the degradation of microplastics (MPs; <5 mm) in different environments, particularly their adsorption characteristics for coexisted metal pollutants remains to be elucidated. Thus, this study investigated the effects of aging MPs, including polyamide (mPA), polyethylene terephthalate (mPET), polystyrene (mPS), and polyvinyl chloride (mPVC) for 3 months under UVA irradiation in four environmental media (air, seawater, sand, and soil) and adsorption of heavy metals (Cu, Cd) onto seawater-aged mPS and mPVC. The results showed that surface morphological changes, including cracks, oxidized particles, and wrinkles, appeared on aged MPs. The heavy metal adsorption capacity decreased in the order aged mPVC > aged mPS > unaged mPS > unaged mPVC, and the Cu²⁺ and Cd²⁺ ions competed for active adsorption sites on the MPs surfaces. Overall, the aging environment affected the physical and chemical properties of MPs and the aging of MPs enhanced their adsorption of coexisting metals tested.

The changes of available forms of heavy metals would affect their corresponding ecological risks in sediments. The distribution of chemical fractions of heavy metals in sediment profiles from Chunfeng Lake estuary was investigated and then a prediction model for potential ecological risk index (PMRI) was proposed to forecast the changes of ecological risks caused by the aging process of metals in sediments. The results show that the estuarine sediments were polluted by As and Cd. The proportions of available metals were generally decreased with depth, while those of the residual forms showed an opposite trend. The aging rates of Cd and As were found to be 0.21 and 0.12%/year, respectively. The PMRI model showed that the total ecological risk of metals in sediments decreased from moderate to low risk level (<150) after 25 years, while cadmium would need 47 years in contrast to the 15 years for As.