Soil contamination with cadmium (Cd) has become a serious problem, adversely affecting food safety and human health. Effective methods are urgently needed to alleviate toxicity of Cd in plants. In this study, a nine-week continuous pot experiments was conducted to explore the effectiveness of the different nano iron oxide (α-Fe₂O₃, γ-Fe₂O₃, Fe₃O₄) alone and combined with biochar in muskmelon grown on a Cd-contaminated soil. The antioxidant system, chlorophyll, soluble protein, other physiological indexes of muskmelon leaves and the distribution of Cd in matrix soil, leaves and fruit were detected. The results showed that Cd was readily absorbed by plants and caused oxidative stress on plants, while biochar, α-Fe₂O₃ nanoparticles (NPs) and their mixture group (BFe1 group) could significantly improve it. Specifically, the three treatments reduced the Cd content of the fruit by 19.51–78.86%, reduced the Cd content of leaves by 15.44–36.23% and 22.36–31.77% in weeks 3 and 5, respectively. For the activity of enzymes, three treatments decreased superoxide dismutase (SOD) activity and catalase (CAT) activity by 3.41–38.57% and 24.27–30.33% in week 7, respectively. So BFe1 group application immobilized Cd in soil and reduced Cd partitioning in the aboveground tissues. Overall the combination of biochar and α-Fe₂O₃ NPs can alleviate Cd toxicity in muskmelon and can protect human beings from Cd exposure.

The neonicotinoid imidacloprid (IMI) is one of the most extensively applied neuro-active insecticides worldwide and continues to enter surface waters in many countries despite a recent ban for outdoor use in the EU. Yet little is known about ecotoxicological effects on non-target benthic freshwater species exposed to environmentally relevant concentrations of IMI and its marketed products. The aim of the present study was to narrow this gap by assessing effects of pure IMI and its commercial formulation Confidor® on the aquatic oligochaete Lumbriculus variegatus, a key species in freshwater sediments. To this end, we determined dose-response relationships in 24 h toxicity tests, bioconcentration during 24 h and 5 d of exposure to 0.1, 1 and 10 μg IMI L⁻¹, and physiological stress responses by measuring glutathione S-transferase, glutathione reductase and catalase activity in the same conditions. Maximum neonicotinoid concentrations reported from the field were lethal to L. variegatus within 24 h (LC₅₀ of 65 and 88 μg IMI L⁻¹ in pure form and as active ingredient of Confidor®, respectively). At sub-lethal exposure concentrations, tissue content of IMI significantly increased with exposure time. The observed bioconcentration factors (BCFs) were far above the water octanol coefficient (KOW), indicating a potentially large underestimation of IMI bioaccumulation when based on KOW. Activities of biotransformation and antioxidant enzymes indicated attempts of L. variegatus to counter xenobiotic-triggered oxidative stress to very low IMI and Confidor® concentrations. Together, our data add significantly to growing evidence that the continued proliferation of neonicotinoids require increased efforts in environmental risk assessment, especially in view of species-specific differences in sensitivities to the insecticide and possibly to additives of commercial formulations.

Long-term CO₂ and PM₂.₅ measurements in urban areas have important impacts on understanding the roles of urbanization in climate change and air pollution. From 2009 to 2017, CO₂ fluxes were measured by the eddy covariance (EC) system at a height of 140 m on the Beijing Meteorological Tower. The CO₂ fluxes followed a typical two-peak diurnal pattern all year round. The PM₂.₅ concentrations followed a similar diurnal pattern as the CO₂ fluxes in summer but a different diurnal pattern in winter (low in the day and high at night). On a seasonal time scale, both the CO₂ fluxes and the PM₂.₅ concentrations showed a pronounced seasonal variation (high in winter and low in summer). The spatial variations in CO₂ fluxes were dominated by the prevailing land use types within the flux footprint, particularly dense residential areas and heavy traffic roads. On both diurnal and annual time scales, the urban underlying surface was a net source of CO₂. The 9-year average annual total CO₂ flux was 36.4 kg CO₂·m⁻² yr⁻¹. Depending on the yearly prevailing wind direction, the effect of the heterogeneity correction on the annual total CO₂ fluxes based on the gap-filled dataset could reach up to 3.5%. Over the 9-year period, both the CO₂ fluxes and the PM₂.₅ concentrations exhibited a declining interannual trend, and CO₂ fluxes could account for 64% of the interannual variability in PM₂.₅ concentrations. In summer, emissions were more likely to control the interannual variability in PM₂.₅ concentrations, whereas in winter, meteorological conditions had a greater impact on the interannual variability in PM₂.₅ concentrations.

Isoprene, formaldehyde and acetaldehyde are important reactive organic compounds which strongly impact atmospheric oxidation processes and formation of tropospheric ozone. Monsoon meteorology and the topography of Himalayan foothills cause surface emissions to get rapidly transported both horizontally and vertically, thereby influencing atmospheric processes in distant regions. Further in monsoon, Indo-Gangetic Plain is a major rice growing region of the world and daytime hourly ozone can frequently exceed phytotoxic dose of 40 ppb O₃. However, the sources and ambient variability of these compounds which are potent ozone precursors are unknown. Here, we investigate the sources and photochemical processes driving their emission/formation during monsoon season from a sub-urban site at the foothills of the Himalayas. The measurements were performed in July, August and September using a high sensitivity mass spectrometer. Average ambient mixing ratios (±1σ variability) of isoprene, formaldehyde, acetaldehyde, and the sum of methyl vinyl ketone and methacrolein (MVK+MACR), were 1.4 ± 0.3 ppb, 5.7 ± 0.9 ppb, 4.5 ± 2.0 ppb, 0.75 ± 0.3 ppb, respectively, and much higher than summertime values in May. For isoprene these values were comparable to mixing ratios observed over tropical forests. Surprisingly, despite occurrence of anthropogenic emissions, biogenic emissions were found to be the major source of isoprene with peak daytime isoprene driven by temperature (r ≥ 0.8) and solar radiation. Photo-oxidation of precursor hydrocarbons were the main sources of acetaldehyde, formaldehyde and MVK+MACR. Ambient mixing ratios of all the compounds correlated poorly with acetonitrile (r ≤ 0.2), a chemical tracer for biomass burning suggesting negligible influence of biomass burning during monsoon season. Our results suggest that during monsoon season when radiation and rain are no longer limiting factors and convective activity causes surface emissions to be transported to upper atmosphere, biogenic emissions can significantly impact the remote upper atmosphere, climate and ozone affecting rice yields.

As inland freshwaters act as a major transport pathway for marine microplastic pollution, microplastic pollution in freshwater systems has recently received growing attention. However, the role of environmental and spatial factors in shaping the distribution and characteristics of microplastic pollution in reservoir ecosystems is not well understood. Here, we studied microplastic pollution in the surface water of the Yulin River, a typical tributary of the upper reaches of the Three Gorges Reservoir (TGR). The abundance of microplastics were 1.30 × 10⁻², 1.95 × 10⁻¹ and 3.60 × 10⁻¹ items/L in the mainstream, tributaries and bays of the Yulin River, respectively. Polyethylene, polypropylene, and polystyrene were identified as the predominant types. The most common shapes were line/fiber and foam. Small-sized particles dominated the collected microplastics. Aged surface was identified by scanning electron microscopy and X-ray photoelectron spectroscopy. The microplastics in the Yulin River were largely of secondary origin. Microplastic pollution varied in space. The abundance of microplastic was higher upstream reaches than downstream, which was correlated with anthropogenic activity. The backwater of the TGR increased the abundance of microplastic in the estuary of the Yulin River. The abundance of microplastic was negatively correlated with the channel width. This study is helpful for understanding the characterics and distribution of microplastics in reservoir ecosystems within underdeveloped area, and can thereby inform well-directed strategies to mitigate microplastic pollution.

The effect of microplastics (MP) exposure on the chironomid species Chironomus riparius Meigen, 1804 was investigated using the OECD sediment and water toxicity test. Chironomid larvae were exposed to an environmentally relevant low microplastics concentration (LC), a high microplastics concentration (HC) and a control (C). The LC was 0.007 g m⁻² on the water surface + 2 g m⁻³ in the water column + 8 g m⁻² in the sediment, and the HC was 10 X higher than this for each exposure. The size of the majority of the manufactured microplastic pellets varied between 20 and 100 μm. The MP mixture consisted of: polyethylene-terephtalate (PET), polystyrene (PS), polyvinyl-chloride (PVC) and polyamide (PA) in a ratio of 45%: 15%: 20%: 20%, respectively, for the sediment exposure; 100% polyethylene for the water column exposure; and 50% polyethylene: 50% polypropylene for the water surface exposure. Different endpoints were monitored, including morphological changes in the mandibles and mentums of 4th instar larvae, morphological changes in the wings, mortality, emergence ratio, and developmental time. A geometric morphometric analysis showed a tendency toward widening of the wings, elongation of the mentums and changing the shape of the mandibles in specimens exposed to both concentrations of microplastics. The development time of C. riparius was significantly prolonged by the MP treatment: 13.8 ± 0.5; 14.4 ± 0.6; and 15.3 ± 0.4 days (mean ± SD) in the C, LC, and HC, respectively. This study indicates that even environmentally relevant concentrations of MP mixture have a negative influence on C. riparius, especially at the larval stage.

Antibiotic resistance genes (ARGs) and antibiotic resistant bacteria (ARB) have become a critical global public health issue in this century. There is increasing evidence for the presence and transmission of ARGs by air transmission. In this research, ARGs and ARB in air conditioner filter dust (AC dust) and urine samples from 55 kindergarten children in 17 kindergartens and nearby 10 soil samples in Hong Kong were analyzed. The results showed the presence of 16 ARG subtypes and the mobile genetic element (MGE) intI1 in AC dust, and 12 ARG subtypes in the soil samples. ARGs presenting resistance to sulfonamide (6.9 × 10⁻³–0.17) (expressed as relative abundance of the 16 S rRNA genes) were most abundant followed by macrolides (1.8 × 10⁻³–3.3 × 10⁻²), sul1, sul2 (sulfonamide), ermF (macrolides) and intI1 genes in AC dust in 17 kindergartens. For soil samples, 12 ARG subtypes and the intI1 were detected, and the genes providing resistance to sulfonamide (1.6 × 10⁻³–2.7 × 10⁻¹) were the most abundant ARGs in the 10 soil samples, followed by tetracycline (ND–1.4 × 10⁻²). Multi-resistant bacteria with sul1, sul2, intI1, or tetQ were detected in all AC dust samples and some urine samples. Based on bacterial genera and ARG co-occurrence network analysis and Hong Kong’s special geographical location and cultural environment, there might be two origins for the ARGs detected in the kindergartens: β-lactam/macrolide ARGs mainly derived from human medicine use and tetracycline/sulfonamide ARGs mainly from other areas, as well as IntI1 may play a role in the spread of ARGs in Hong Kong. The widely detection of ARGs in AC dust in kindergartens in Hong Kong highlights the need for the improvement of management measures.

Fourteen perfluoroalkyl substances (PFASs) in fishery organism, surface seawater, river water, rainwater, and wastewater samples collected from Jiaozhou Bay (JZB) in China and its surrounding area were determined to understand their contamination status, sources, health risk, and causes of spatiotemporal variations in the aquatic environment of a temperate bay adjacent to a metropolis. The total concentration of PFASs in 14 species of fishery organisms ranged from 1.77 ng/g to 31.09 ng/g wet weight, and perfluorooctane sulfonate (PFOS) was the dominant PFAS. ∑PFASs concentration in surface seawater ranged from 5.54 ng/L to 48.27 ng/L over four seasons, and dry season (winter and spring) had higher levels than wet season (summer and autumn). Perfluorooctanoic acid (PFOA) was the predominant individual PFAS in seawater, indicating that notorious C8 homologs remained the major PFASs in this region. The seasonal variation in seawater concentrations of three major PFASs, namely, PFOA, perfluoroheptanoic acid, and perfluorononanoic acid, was similar to that of ∑PFASs. However, the seasonal variation of PFOS concentration was different from that of ∑PFASs, with the lowest in winter and the highest in spring. In general, seasonal variations of terrigenous input and water exchange capacity were the main reasons for the spatiotemporal variation of PFASs in the aquatic environment of JZB. Moreover, bioselective enrichment for individual PFAS affected the partition of PFASs in different environment medium. Wet precipitation, sewage discharge, and surface runoff were the main sources of PFASs in this area. Nevertheless, the contribution of different sources to individual PFAS indicated a clear difference, and wastewater and river water were not consistently the most important source for every PFAS. Preliminary risk assessment revealed that the consumption of seafood, especially fish, from JZB might pose a certain extent of health risk to local consumers based on their estimated daily intake of PFASs.

The abnormality in thyroid hormone modulation in developmental fish, vulnerable to per- and polyfluorinated substances, is of particular concerns for the alternative substances. Juvenile rare minnows, were exposed to chlorinated polyfluoroalkyl ether sulfonates (Cl-PFESAs), the novel alternatives to perfluorooctane sulfonate (PFOS), for 4 weeks followed by 12 weeks of depuration. Half lives were determined to be 33 d, 29 d, and 47 d for total Cl-PFESAs, C8 Cl-PFESA and C10 Cl-PFESA, respectively. Preliminary toxicity test suggested that Cl-PFESAs are moderately toxic to Rare minnow with a LC50 of 20.8 mg/L (nominal concentration） after 96 h of exposure. In the chronic toxicity test, fishes were exposed to Cl-PFESAs at geometric mean measured concentrations of 86.5 μg/L, 162 μg/L and 329 μg/L. In juvenile fishes exposed to Cl-PFESAs for 4 weeks, gene profile sequencing analysis identified 3313 differentially expressed genes, based on which pathways regulating thyroid hormone synthesis and steroid synthesis were enriched. Both whole body total and free 3,5,3′-triiodothyronine (T3) levels were significantly increased. mRNA expression of genes regulating thyroid hormone synthesis (corticotropin-releasing hormone (CRH), thyroid-stimulating hormone (THS), sodium/iodide symporter (NIS), thyroglobulin (TG), and thyroid peroxidase (TPO), transport (transthyretin,TTR), deiodinase (Dio1, Dio2) and receptor (TRα and TRβ) were decreased. Uridinediphosphate glucoronosyl-transferases (UGT1A) gene, regulating THs metabolism, was also decreased. In adult fish, thyroid hormone and genes expression in hypothalamic-pituitary-thyroid axis remained at disturbed levels after 12 weeks of depuration without exposure. Chronic developmental exposure to Cl-PFESAs caused persistent thyroid hormone disrupting effects in fish, highlighting a necessity of comprehensive ecological risk assessment.

Evidence of health effects following early life exposure to short-to-medium duration of high pollution levels is extremely limited.We aimed to evaluate the associations between: 1. intrauterine exposure to fine particulate matter (PM2.5) from coal mine fire emissions and the frequencies of general practitioner attendances and dispensations of prescribed asthma inhalers, steroid skin creams, and antibiotics during the first year of life; 2. infant exposure and those outcomes during the year following the fire.All participants were recruited from the Latrobe Valley of Victoria, Australia. Participants’ 24-h average and hourly peak mine fire-specific PM2.5 exposures from 09/02/2014 to 31/03/2014 were estimated using chemical transport modelling. Outcome data were obtained from the Australian Medicare Benefits Schedule and Pharmaceutical Benefits Scheme from each child’s birth to 31/12/2016. We used negative binomial and logistic regression models to independently assess risks of the outcomes associated with every 10 and 100 μg m−3 increase in average or peak PM2.5 exposure, respectively, while adjusting for potential confounders.We included 286 of 311 children whose parents consented to be linked, comprising 77 with no exposure, 88 with intrauterine exposure and 121 with exposure in infancy. 10- and 100- μg m−3 increases in average and peak PM2.5 exposure during infancy were associated with greater incidence of antibiotics being dispensed during the year following the fire: the adjusted incidence rate ratios were 1.24 (95% CI 1.02, 1.50, p = 0.036) and 1.14 (1.00, 1.31, p = 0.048) respectively. No other significant associations were observed.Exposure to coal mine fire emissions during infancy was associated with increased dispensing of antibiotics. This could reflect increased childhood infections or increased prescriptions of antibiotics in the year following the fire.