Frequent drought events and particulate matter pollution from vehicular exhaust seriously affect urban plant growth and provisioning of ecological services. Yet, how plants respond physiologically and morphologically to these two combined stressors remains unknown. Here, we assessed particle retention dynamics and plant morphology and physiology of Euonymus japonicus Thunb. var. aurea-marginatus Hort. under continuous drought with severe exhaust exposure. Our results showed that continuous drought insignificantly lowered particle retention in each of three size fractions by 1.02 μg·cm⁻² on average in the first 28 days, but significantly lowered total particle retention by 35.75 μg·cm⁻² on the 35th day. We observed evident changes in morphology, leaf mass per area (LMA), pigments, gas exchange in all stressed plants. Compared with single stress, combined drought and pollution caused earlier yellowing and shedding of old leaves, significantly lowered LMA by 1.21 mg·cm⁻², caused a greater decline in pigments and net photosynthetic rate (Pₙ). Large particles may mainly explain pigment reduction, lower weekly LMA increases, and stomatal restriction, while coarse particles may be the main drivers of the decline in Pₙ. Continuous drought mediated the influence of all three particle sizes on some parameters, such as weakening the impact of total particles on LMA, strengthening the impact of fine particles on photosynthesis. Our findings suggest that drought accelerates the physiological responses of plants to exhaust pollution. Under controlled severe exhaust pollution conditions, the optimal time to maintain high particle retention during continuous drought without decline in physiological conditions for E. japonicus var. aurea-marginatus was 14 days. Some additional interventions after 14 days (it could be postponed appropriately under field conditions) may help ensure healthy growth of plants and retention of particulate matter.

Arsenic is a potent toxicant, and long-term exposure to inorganic arsenic causes lung damage. M2 macrophages play an important role in the pathogenesis of pulmonary fibrosis. However, the potential connections between arsenic and M2 macrophages in the development of pulmonary fibrosis are elusive. C57BL/6 mice were fed with drinking water containing 0, 10 and 20 ppm arsenite for 12 months. We have found that, in lung tissues of mice, arsenite, a biologically active form of arsenic, elevated H19, c-Myc, and Arg1; decreased let-7a; and caused pulmonary fibrosis. For THP-1 macrophages (THP-M) and bone-marrow-derived macrophages (BMDMs), 8 μM arsenite increased H19, c-Myc, and Arg1; decreased let-7a; and induced M2 polarization of macrophages, which caused secretion of the fibrogenic cytokine, TGF-β1. Down-regulation of H19 or up-regulation of let-7a reversed the arsenite-induced M2 polarization of macrophages. Arsenite-treated THP-M and BMDMs co-cultured with MRC-5 cells or primary lung fibroblasts (PLFs) elevated levels of p-SMAD2/3, SMAD4, α-SMA, and collagen I in lung fibroblasts and resulted in the activation of lung fibroblasts. Knockout of H19 or up-regulation of let-7a in macrophages reversed the effects. The results indicated that H19 functioned as an miRNA sponge for let-7a, which was involved in arsenite-induced M2 polarization of macrophages and induced the myofibroblast differentiation phenotype by regulation of c-Myc. In the sera of arseniasis patients, levels of hydroxyproline and H19 were higher, and levels of let-7a were lower than levels in the controls. These observations elucidate a possible mechanism for arsenic exposure-induced pulmonary fibrosis.

Microplastic pollution in marine environments and organisms has received a great deal of international attention. However, the long-term field studies of microplastics are rare. Here, we assessed annual variation in microplastic abundance in the Maowei Sea, a classic mariculture bay in southern China, and analyzed the long-term accumulation in oyster tissues. U-shaped time trends of microplastics in water were observed from January to December in 2018 in the estuarine region, inner bay, and mouth bay sites, representing an inverse relationship with the local rainfall patterns. The common microplastic particles in Maowei Sea are PET/PE fibers, and polystyrene foams, which are mainly related to textile pollution and fishery activities. After one year of continuous monitoring, we did not find accumulation of microplastics in the whole soft tissues of oyster after 10% KOH digestion. No significant correlation of microplastic abundances between water and oysters was observed. The microplastic abundance in oyster was correlated with some environmental variables (i.e. salinity, pH, nutrients and total organic carbon) of the surrounding water following Spearman correlation analysis. The microplastic levels in oysters could probably be influenced by the environmental variables.

Chinese children have been exposed to high level of lead due to polluted air, dust, contaminated foods and water, etc. In this research, we investigated published blood lead levels (BLLs) reflecting 1,057,832 Chinese children aged at 0–12 and teenagers aged at 13–18 in the past 30 years (1991–2020). The data mining and estimation were performed innovatively by Monte Carlo simulation to remedy the skewed distribution-induced bias. The temporal trend of Chinese children’s BLLs showed an obvious decrease in the past decades from 88.74 μg/L (Geometric SD = 4.09) during 1991–1995 to 27.32 μg/L (Geometric SD = 4.18) during 2016–2020. This study also indicated that children’s BLLs of Yunnan, Guizhou, Shanxi were at relatively high levels and most provinces showed a downward trend. Chinese boys aged at 1–18 years old had higher BLLs (GM: 44.03 μg/L) compared to girls (GM: 41.32 μg/L) (p < 0.001). At different age groups, Chinese children’s BLLs were 42.04 μg/L (1–3 years old), 52.88 μg/L (4–6 years old), 50.49 μg/L (7 and above years old), respectively. Although the BLLs of Chinese children exhibited a continuous declined trend in the past 30 years, it was still higher than that in developed countries, which indicated that more efforts are needed in children’s BLLs control.

Herein, we report the optimization of nitrogen (N) doping in TiO₂ nanotubes to achieve the enhanced photocatalytic efficiencies in degradation of dye and H₂ gas evolution under solar light exposure. TiO₂ nanotubes have been produced via hydrothermal process and N doping has been tuned by varying the concentration of urea, being the source for N, by solid-state dispersion process. The structural analysis using XRD showed the characteristic occupancy of N into the structure of TiO₂ and the XPS studies showed the existence of Ti–N–Ti network in the N-doped TiO₂ nanotubes. The obtained TEM images showed the formation of 1D tube-like structure of TiO₂. Diffuse reflectance UV–Vis absorption spectra demonstrated that the N-doped TiO₂ nanotubes can efficiently absorb the photons of UV–Vis light of the solar light. The optimized N-doped TiO₂ nanotubes (TiO₂ nanotubes vs urea @ 1:1 ratio) showed the highest degradation efficiency over methyl orange dye (∼91% in 90 min) and showed the highest rate of H₂ evolution (∼19,848 μmol h⁻¹.g⁻¹) under solar light irradiation. Further, the recyclability studies indicated the excellent stability of the photocatalyst for the durable use in both the photocatalytic processes. The observed efficiency was ascribed to the optimized doping of N-atoms into the lattices of TiO₂, which enhanced the optical properties by forming new energy levels of N atoms near the valence band maximum of TiO₂, thereby increased the overall charge separation and recombination resistance in the system. The improved reusability of photocatalyst is attributed to the doping-induced structural stability in N-doped TiO₂. From the observed results, it has been recognized that the established strategy could be promising for synthesizing N-doped TiO₂ nanotubes with favorable structural, optical and photocatalytic properties towards dye degradation and hydrogen production applications.

Forest and agricultural land use affects the concentration and composition of dissolved organic carbon (DOC) in streams and rivers. To elucidate the impacts of forest and agricultural land use on stream DOC during storm events, we investigated DOC concentration ([DOC]), optical properties of dissolved organic matter (DOM), and Δ¹⁴C-DOC in both forest- and agriculture-dominated headwater streams in South Korea in the summer of 2012. One forested and five agricultural streams were investigated. During storms, the peak [DOC] of forest stream increased to 5.8 mg L⁻¹, approximately two times larger than that of the most agricultural stream (3.2 mg L⁻¹), demonstrating the weaker storm responses of the [DOC] of agricultural streams to hydrological change. Five PARAFAC components were identified, including three terrestrial humic-like substances (C1, C2, C3), one microbial humic substance (C4), and one microbial protein-like substances (C5). The mean (C4+C5)/(C1+C2+C3) of all storm events at the most agricultural stream was 1.5 times larger than that of the most forested stream, suggesting that more protein-like DOM is exported from agricultural watersheds. Whereas a forest stream was primarily composed of terrestrially derived and ¹⁴C-enriched modern DOC, the ¹⁴C-age of the most agricultural stream was up to ∼1000 years old. The results suggest that agricultural practices could decrease the old organic carbon pools from soils. However, how quickly the aged DOC can be degraded to CO₂ in streams is unknown, warranting future investigation on lability of the aged DOC and their effects on CO₂ evasion from rivers and estuaries downstream.

Assessing the bioavailability of various Sb substances plays a crucial role in human health and the ecological risk assessment of contaminated soils. However, fate, behaviour and bioavailability of different Sb compounds in soils are insufficiently known. Therefore, in this present study, the effects of soil properties and ageing on bioavailability of four different Sb compounds (C₈H₄K₂O₁₂Sb₂, Sb₂S₃, Sb₂O₃ and Sb₂O₃ nanoparticles) were evaluated during 120 days ageing time. A black soil (BS) with approximately 12% organic matter (OM) and a red soil (RS) with less than 1% OM were amended with 1000 mg Sb kg⁻¹ of different Sb compounds and subjected to single extractions with distilled (DI) water, 2M HNO₃, Simplified Bioaccessibility Extraction Test (SBET) and a modified Community Bureau of Reference (BCR) sequential extraction method. The results revealed that there are substantial variations in dissolution rate of various Sb sources, depending upon soil type and Sb compound. The amounts of DI water extractability of Sb during the incubation time varied between <1% and 2%, whereas HNO₃ extractable fractions and Sb bioaccessibility at the end of ageing time ranged between about 1%-3% and <1%–9% of the total Sb, with maximum bioaccessibility observed in BS contaminated with C₈H₄K₂O₁₂Sb₂. The residual and labile fractions accounted for 77–93% and 0.1–4% of the total Sb, respectively, indicating that Sb is mostly associated with recalcitrant fractions of the soils. The results of single and sequential extraction studies revealed that source of Sb, ageing time and soil properties can greatly affect the bioavailability of Sb in soils. The findings of this research provide a deeper understanding of the potential risks associated with Sb compounds and highlights the role of site-specific considerations for improving the robustness of toxicity guidelines and long-term management of Sb contaminated sites.

Salinity is a limiting factor in the growth of plants in coastal wetlands. The interaction of halophytes with salt-tolerant endophytes has been one of the major concerns in this area. However, the mechanism by which endophytes promote halophyte growth remains unclear. The growth and physiological responses of Suaeda salsa inoculated with endophytic bacteria (Sphingomonas prati and Sphingomonas zeicaulis) at 0 ‰ and 20 ‰ NaCl were studied. The results showed that Sphingomonas zeicaulis had stronger positive effects on the growth of Suaeda salsa under 0 ‰ NaCl, and Sphingomonas prati performed better under 20 ‰ NaCl. Sphingomonas prati inoculation increased the mean height, root length, fresh weight and dry weight by 45.43%, 9.91%, 82.00% and 102.25%, respectively, compared with the uninoculated treatment at 20 ‰ NaCl. Sphingomonas prati inoculation decreased MDA content by 23.78%, while the soluble sugar and soluble protein contents increased by 15.08% and 12.57%, respectively, compared to the control, at 20 ‰ NaCl. Increases in SOD and CAT in the Sphingomonas prati inoculation were 1.03 and 1.47-fold greater, respectively, than in the Sphingomonas zeicaulis inoculation, under 20 ‰ NaCl. Moreover, Sphingomonas prati and Sphingomonas zeicaulis had antagonistic interactions in Suaeda salsa according to the results of the “interaction equation” (most G values were negative). PCA, clustering analysis and the PLS model revealed two mechanisms for regulating plant salt tolerance by which Sphingomonas prati enhanced Suaeda salsa growth: (1) Sphingomonas prati improved intracellular osmotic metabolism and (2) Sphingomonas prati promoted the production of CAT in the antioxidant enzyme system and retained permeability. This study provides new insight into the comprehensive understanding and evaluation of endophytic bacteria as biological inoculants in plants under salt stress.

The current study for the first time demonstrates the interference of a free-living, N₂-fixing, and nanoparticle (NP) tolerant Azotobacter salinestris strain ASM recovered from metal-polluted soil with tomato plant-metal oxide NPs (ZnO, CuO, Al₂O₃, and TiO₂) interactions in a sandy clay loam soil system with bulk materials as control. Tomato plants were grown till full maturity in soils amended with 20–2000 mg kg⁻¹ of each metal-oxide NP with and without seed biopriming and root-inoculation of A. salinestris. A. salinestris was found metabolically active, producing considerably high amounts of bioactive indole-3-acetic-acid, morphologically unaffected, and with low alteration of cell membrane permeability under 125–1500 μgml⁻¹ of NPs. However, ZnO-NPs slightly alter bacterial membrane permeability. Besides, A. salinestris secreted significantly higher amounts of extracellular polymeric substance (EPS) even under NP exposure, which could entrap the NPs and form metal-EPS complex as revealed and quantified by SEM-EDX. NPs were also found adsorbed on bacterial biomass. EPS stabilized the NPs and provided negative zeta potential to NPs. Following soil application, A. salinestris improved the plant performance and augmented the yield of tomato fruits and lycopene content even in NPs stressed soils. Interestingly, A. salinestris inoculation enhanced photosynthetic pigment formation, flower attributes, plant and fruit biomass, and reduced proline level. Bacterial inoculation also reduced the NP’s uptake and accumulation significantly in vegetative organs and fruits. The organ wise order of NP’s internalization was roots > shoots > fruits. Conclusively, A. salinestris inoculation could be an alternative to increase the production of tomato in metal-oxide NPs contaminated soils.

Seven perfluorinated and polyfluorinated substances (PFASs), namely perfluorononanoic acid (PFNA), perfluorodecanoic acid (PFDA), perfluorooctanoic acid (PFOA), perfluorooctane sulfonic acid (PFOS), perfluoroheptanoic acid (PFHpA), perfluorohexanoic acid (PFHxA), and perfluoro-1,10-decanedicarboxylic acid (PFDDA), were evaluated in urine and hair samples from children (age: 4–6 years, N = 53), airborne particles sampled at 17 kindergartens, and tap water and bottled water samples. All samples were collected in Hong Kong. The analytical results suggested widespread PFAS contamination. All target PFASs were detected in at least 32% of urine samples, with geometric mean (GM) concentrations ranging from 0.18 to 2.97 ng/L, and in 100% of drinking water samples at GM concentrations of 0.18–21.1 ng/L. Although PFOS and PFDDA were not detected in hair or air samples, the other target PFASs were detected in 48–70% of hair samples (GM concentrations: 2.40–233 pg/g) and 100% of air samples (GM concentrations: 14.8–536.7 pg/m³). In summary, the highest PFAS concentrations were detected in airborne particles measured in kindergartens. PFOA was the major PFAS detected in hair, urine, and drinking water samples, while PFOA, PFDA, and PFHpA were dominant in airborne particles. Although a significant difference in PFAS concentrations in hair samples was observed between boys and girls (p < .05), no significant sex-related difference in urinary PFAS or paired PFAS (hair/urine) concentrations was observed.