Development of non-noble metal cluster catalysts, aiming at concurrently high activity and stability, for emission control systems has been challenging because of sintering and overcoating of clusters on the support. In this work, we reported the role of well-dispersed copper nanoclusters supported on TiO₂ in CO oxidation under industrially relevant operating conditions. The catalyst containing 0.15 wt% Cu on TiO₂ (0.15 CT) exhibited a high dispersion (59.1%), a large specific surface area (381 m²/gCᵤ), a small particle size (1.77 nm), and abundant active sites (75.8% Cu₂O). The CO oxidation activity measured by the turnover frequency (TOF) was found to be enhanced from 0.60 × 10⁻³ to 3.22 × 10⁻³ molCO·molCᵤ⁻¹·s⁻¹ as the copper loading decreased from 5 to 0.15 wt%. A CO conversion of approximately 60% was still observed in the supported cluster catalyst with a Cu loading of 5 wt% at 240 °C. No deactivation was observed for catalysts with low copper loading (0.15 and 0.30 CT) after 8 h of time-on-stream, which compares favorably with less stable Au cluster-based catalysts reported in the literature. In contrast, catalysts with high copper loading (0.75 and 5 CT) showed deactivation over time, which was ascribed to the increase in copper particle size due to metal cluster agglomeration. This study elucidated the size-activity threshold of TiO₂-supported Cu cluster catalysts. It also demonstrated the potential of the supported Cu cluster catalyst at a typical temperature range of diesel engines at light-load. The supported Cu cluster catalyst could be a promising alternative to noble metal cluster catalysts for emission control systems.

Exposure to particulate air pollution has been associated with a variety of respiratory, cardiovascular and neurological problems, resulting in increased morbidity and mortality worldwide. Brake-wear emissions are one of the major sources of metal-rich airborne particulate pollution in roadside environments. Of potentially bioreactive metals, Fe (especially in its ferrous form, Fe²⁺) might play a specific role in both neurological and cardiovascular impairments. Here, we collected brake-wear particulate emissions using a full-scale brake dynamometer, and used a combination of magnetic measurements and electron microscopy to make quantitative evaluation of the magnetic composition and particle size of airborne emissions originating from passenger car brake systems. Our results show that the concentrations of Fe-rich magnetic grains in airborne brake-wear emissions are very high (i.e., ~100–10,000 × higher), compared to other types of particulate pollutants produced in most urban environments. From magnetic component analysis, the average magnetite mass concentration in total PM₁₀ of brake emissions is ~20.2 wt% and metallic Fe ~1.6 wt%. Most brake-wear airborne particles (>99 % of particle number concentration) are smaller than 200 nm. Using low-temperature magnetic measurements, we observed a strong superparamagnetic signal (indicative of ultrafine magnetic particles, < ~30 nm) for all of the analysed size fractions of airborne brake-wear particles. Transmission electron microscopy independently shows that even the larger size fractions of airborne brake-wear emissions dominantly comprise agglomerates of ultrafine (<100 nm) particles (UFPs). Such UFPs likely pose a threat to neuronal and cardiovascular health after inhalation and/or ingestion. The observed abundance of ultrafine magnetite particles (estimated to constitute ~7.6 wt% of PM₀.₂) might be especially hazardous to the brain, contributing both to microglial inflammatory action and excess generation of reactive oxygen species.

In general, tire tread rubber compounds contain oleamide for improvement of manufacturing processibility, mold release characterization, and abrasion resistance. Tire tread wear particles (TWPs) are one of major contributors to microplastic emissions. In this study, a novel analytical method for quantification of TWP in microparticles produced on the road (road dust, MPRs) was developed by employing oleamide as a new marker. MPRs were collected at bus stops in autumn, winter, and summer seasons. MPRs of 38–63, 63–106, 106–212, and 212–500 μm obtained by size separation were employed for the analysis. Rubber components for bus and passenger car tire tread compounds were identified using pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS). Oleamide was extracted from the MPRs with acetone and was identified using GC/MS. The oleamide concentration was analyzed using GC equipped with flame ionization detector (FID). The TWP contents of the MPRs were determined using the oleamide concentrations and the reference compound formulations. In order to reduce the sampling errors, each experiment was carried out five times and the results were averaged. The TWP contents of the MPRs were 1.4–4.7 wt% and were different according to the sampling seasons and places. The TWP contents were increased by increasing the traffic volume and the temperature.

The increasing human presence is having an impact on plateau ecosystems, but the special environment and lack of data make it difficult to assess the real ecological risks of pharmaceutical and personal care products (PPCPs) in the river of plateau. The occurrence, distribution and trophic transfer of nineteen PPCPs were investigated in the middle and lower reaches of the Yarlung Zangbo River on the Tibetan Plateau. All the targeted PPCPs were detected in filtrated water, and seventeen PPCPs were detected in the colloid, sediment and suspended particulate matter (SPM). The distribution coefficients of colloid-infiltration water (IFW) were 1–2 orders of magnitude larger than those in the SPM-IFW, which were 1–2 orders of magnitude greater than those in the sediment-IFW. Colloids are sinks for PPCPs with up to 78.55% of the water being in the colloidal phase, in which important factors such as protein and protein-like substances are found. PPCPs in the rivers of the plateau showed high bioaccumulation ability. The fugacity-based bioaccumulation model was established and revealed that the fish in the Tibetan Plateau ingested PPCPs mainly through water instead of food and excreted them mainly through metabolism. In addition, the trophic dilution effect in the food web was observed with trophic magnification factors ranging from 0.06 to 0.22. The positive correlation between the Kd in the colloid-IFW and the bioaccumulation factors implied that natural colloids can not only regulate the behaviour of PPCPs in the environment, but also play an important role in bioaccumulation, which may affect the scientific nature of biological risk assessment.

Thousands of abandoned mines throughout the western region of North America contain elevated total-mercury (THg) concentrations. Mercury is mobilized from these sites primarily due to erosion of particulate-bound Hg (THg-P). Organic matter-based soil amendments can promote vegetation growth on mine tailings, reducing erosion and subsequent loading of THg-P into downstream waterbodies. However, the introduction of a labile carbon source may stimulate microbial activity that can produce methylmercury (MeHg)—the more toxic and bioaccumulative form of Hg. Our objectives were to investigate how additions of different organic matter substrates impact Hg mobilization and methylation using a combination of field observations and controlled experiments. Field measurements of water, sediment, and porewater were collected downstream of the site and multi-year monitoring (and load calculations) were conducted at a downstream gaging station. MeHg production was assessed using stable isotope methylation assays and mesocosm experiments that were conducted using different types of organic carbon soil amendments mixed with materials from the mine site. The results showed that >80% of the THg mobilized from the mine was bound to particles and that >90% of the annual Hg loading occurred during the period of elevated discharge during spring snowmelt. Methylation rates varied between different types of soil amendments and were correlated with the components of excitation emission matrices (EEMs) associated with humic acid fractions of organic matter. The mesocosm experiments showed that under anoxic conditions carbon amendments to tailings could significantly increase porewater MeHg concentrations (up to 13 ± 3 ng/L). In addition, the carbon amendments significantly increased THg partitioning into porewater. Overall, these results indicate that soil amendment applications to reduce surface erosion at abandoned mine sites could be effective at reducing particulate Hg mobilization to downstream waterbodies; however, some types of carbon amendments can significantly increase Hg methylation as well as increase the mobilization of dissolved THg from the site.

Lake sediments are widely used as environmental archives to reconstruct past changes in contaminants deposition, provided that they remain immobile after deposition. Arsenic (As) is a redox-sensitive element that may be redistributed in the sediments during early diagenesis, for instance along with iron and manganese, and thus depth profiles of As might not provide a reliable, unaltered record of past deposition. Here, we use inverse diagenetic modelling to calculate fluxes of As across the sediment-water interface and interpret As sedimentary records in eight lakes along a 80 km transect from the Giant and Con mines, Northwest Territories, Canada. The sediment cores were dated using ²¹⁰Pb methods and analyzed for solid-phase and porewater As, Fe, Mn and organic C concentrations. We reconstructed the history of As deposition by correcting for the varying mobility patterns and calculated contemporary As deposition fluxes. Correction for diagenesis was substantial for three of the eight lakes, suggesting that lakes with lower sedimentation rates, which allows longer residence of As within the reactive zones defined by the model, enhance the influence of diagenesis. Results show that solid phase As peaks coincides with the period of high emissions from past gold ore roasting activities. Results also show that sediments sustained present-day As fluxes to the water column of study lakes within 50 km of the mines, while sediment in study lakes further than 50 km acted as As sinks instead.

Emissions reductions in upwind areas can influence the PM₂.₅ concentrations in downwind areas via long-range transport. However, few studies have assessed the impact of upwind PM₂.₅ precursor controls on changes in downwind PM₂.₅ concentrations. In this study, we analyzed the overall impact of PM₂.₅ precursor emission controls in upwind areas on PM₂.₅ in downwind areas with two types of impacts: “direct impact” and “cross impact.” The former refers to PM₂.₅ changes in downwind areas due to the transported PM₂.₅ itself, whereas the latter represents PM₂.₅ changes due to reactions between the transported gaseous precursors and intermediates (i.e., HNO₃) originating from upwind areas and locally emitted precursors (i.e. NH₃) in the downwind areas. As a case study, we performed air quality modeling for Northeast Asia for January 15–17, 2016 by setting China and South Korea as the upwind and downwind areas, respectively. To account for potential spatiotemporal variations in NH₃ emissions in downwind areas, we considered two NH₃ conditions. When NOx emissions in China were reduced by 35%, in downwind areas the PM₂.₅ concentrations decreased by 2.2 μg/m³ under NH₃-rich conditions, while PM₂.₅ concentrations increased by 2.3 μg/m³ under NH₃-poor conditions. The direct impact increased by 4.0 μg/m³ in both cases due to upwind NOₓ disbenefit effects. However, the cross impacts led to a PM₂.₅ decrease of 6.2 μg/m³ under NH₃-rich conditions versus a PM₂.₅ increase of 1.7 μg/m³ under NH₃-poor conditions. We noted that PM₂.₅ concentrations in the downwind areas may not improve unless a cross impact outweighs a direct impact. This may be one of the reasons why South Korea PM₂.₅ concentrations have not declined despite efforts by China to reduce their PM₂.₅ precursor emissions.

Vertical measurements of ozone (O₃) within the 3000-m lower troposphere were obtained using an O₃ lidar to investigate the contribution of the interactions between the transport and boundary layer processes to the surface O₃ levels in urban Shanghai, China during July 23–28, 2017. An extremely severe pollution episode with a maximum hourly O₃ mixing ratio of 160.4 ppb was observed. In addition to enhanced local photochemical production, both downward and advection transport in the lower troposphere may have played important roles in forming the pollution episode. The O₃-rich air masses in the lower free troposphere primarily originated from central China and the northern Yangtze River Delta (YRD) region. The downward transport of O₃ from the lower free troposphere may have an average contribution of up to 49.1% to the daytime (09:00–16:00 local time) surface O₃ in urban Shanghai during the pollution episode (July 23–26, 2017). As for the advection transport, large amounts of O₃ were transported outward from Shanghai in the planetary boundary layer under the influence of southeasterly winds during the field study. In this condition, the boundary-layer O₃ that was transported downward from the free troposphere in Shanghai could be transported back to the northern YRD region and accumulated therein, leading to the occurrence of severe O₃ pollution events over the whole YRD region. Our results indicate that effective regional emission control measures are urgently required to mitigate O₃ pollution in the YRD region.

The aggregation kinetics of fragmental polyethylene glycol terephthalate (PET) nanoplastics under various chemistry conditions in aqueous environment were firstly investigated in this work. The aggregation of PET nanoplastics increased with increasing electrolyte concentrations and decreasing solution pH, which became stronger with the presence of divalent cations (e.g. Ca²⁺ and Mg²⁺) than that of monovalent cations (e.g. Na⁺ and K⁺). The effect of cations with the same valence on the aggregation of PET nanoplastics was similar. The measured critical coagulation concentrations (CCC) for PET nanoplastics at pH 6 were 55.0 mM KCl, 54.2 mM NaCl, 2.1 mM CaCl₂ and 2.0 mM MgCl₂, which increased to 110.4 mM NaCl and 5.6 mM CaCl₂ at pH 10. In addition, the aggregation of PET nanoplastics was significantly inhibited with the presence of humic acid (HA), and the CCC values increased to 558.8 mM NaCl and 12.3 mM CaCl₂ (1 mg L⁻¹ HA). Results from this study showed that the fragmental PET nanoplastics had the quite higher CCC values and stability in aqueous environment. In addition, the aggregation behaviors of PET nanoplastics can be successfully predicted by the Derjguin Landau Verwey Overbeek (DLVO) theory.

Tropospheric (ground-level) ozone is a harmful phytotoxic pollutant, and can have a negative impact on crop yield and quality in sensitive species. Ozone can also induce visible symptoms on leaves, appearing as tiny spots (stipples) between the veins on the upper leaf surface. There is little measured data on ozone concentrations in Africa and it can be labour-intensive and expensive to determine the direct impact of ozone on crop yield in the field. The identification of visible ozone symptoms is an easier, low cost method of determining if a crop species is being negatively affected by ozone pollution, potentially resulting in yield loss. In this study, thirteen staple African food crops (including wheat (Triticum aestivum), common bean (Phaseolus vulgaris), sorghum (Sorghum bicolor), pearl millet (Pennisetum glaucum) and finger millet (Eleusine coracana)) were exposed to an episodic ozone regime in a solardome system to monitor visible ozone symptoms. A more detailed examination of the progression of ozone symptoms with time was carried out for cultivars of P. vulgaris and T. aestivum, which showed early leaf loss (P. vulgaris) and an increased rate of senescence (T. aestivum) in response to ozone exposure. All of the crops tested showed visible ozone symptoms on their leaves in at least one cultivar, and ozone sensitivity varied between cultivars of the same crop. A guide to assist with identification of visible ozone symptoms (including photographs and a description of symptoms for each species) is presented.