Nitrogen dioxide (NO₂) is an important air pollutant that causes direct harms to the environment and human health. Ground NO₂ mapping with high spatiotemporal resolution is critical for fine-scale air pollution and environmental health research. We thus developed a spatiotemporal regression kriging model to map daily high-resolution (3-km) ground NO₂ concentrations in China using the Tropospheric Monitoring Instrument (TROPOMI) satellite retrievals and geographical covariates. This model combined geographically and temporally weighted regression with spatiotemporal kriging and achieved robust prediction performance with sample-based and site-based cross-validation R² values of 0.84 and 0.79. The annual mean and standard deviation of ground NO₂ concentrations from June 1, 2018 to May 31, 2019 were predicted to be 15.05 ± 7.82 μg/m³, with that in 0.6% of China’s area (10% of the population) exceeding the annual air quality standard (40 μg/m³). The ground NO₂ concentrations during the coronavirus disease (COVID-19) period (January and February in 2020) was 14% lower than that during the same period in 2019 and the mean population exposure to ground NO₂ was reduced by 25%. This study was the first to use TROPOMI retrievals to map fine-scale daily ground NO₂ concentrations across all of China. This was also an early application to use the satellite-estimated ground NO₂ data to quantify the impact of the COVID-19 pandemic on the air pollution and population exposures. These newly satellite-derived ground NO₂ data with high spatiotemporal resolution have value in advancing environmental and health research in China.

Organotin compounds are highly toxic environmental pollutants with neurotoxic and endocrine-disrupting effects. They are potent inhibitors of glutathione transferases (GSTs), thus impeding their detoxication and antioxidant functions. Several GSTs, including equine GST A3-3 (EcaGST A3-3), exhibit steroid double-bond isomerase activity and are involved in the biosynthesis of testosterone and progesterone. We have performed enzyme kinetics analyses of the inhibition of EcaGST A3-3 by organotin compounds. We have also solved crystal structures of EcaGST A3-3 in complexes with glutathione, and with glutathione together with covalently bound triethyltin. Our structural data indicate that the tin atom forms strong bonds with a covalent character not only with the glutathione, but also with a tyrosyl residue of the enzyme itself, thereby preventing the release of the glutathione-organotin adduct and completely blocking the enzyme function. This work presents a structural basis for the general mechanism of GST inhibition by organotin compounds and contributes to the understanding of their neurotoxic and endocrine disrupting effects.

Substantial heterogeneities have been found in previous estimations of the risk from dietary exposures to persistent organic pollutants (POPs) in China, mainly due to spatiotemporal variations. To comprehensively evaluate the dietary risks of POPs listed in the Stockholm Convention, more than 27,580 data records from 753 reports published over the last three decades were examined. Respectively, for various food categories, the results obtained for the range of mean concentrations of POPs are as follows: total dichlorodiphenyltrichloroethanes (DDTs: 1.4–27.1 μg/kg), hexachlorocyclohexanes (HCHs: 1.8–29.3 μg/kg), polybrominated diphenyl ethers (PBDEs: 0.046–2.82 μg/kg), polychorinated biphenyls (PCBs: 0.05–7.57 μg/kg), polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD&Fs: 2.9–210 pg toxic equivalent (TEQ)/kg), perfluorooctanoic acid (PFOA: 0.02–0.97 μg/kg), perfluoroctane sulfonate (PFOS: 0.00082–2.76 μg/kg) and short-chain chlorinated paraffins (SCCPs: 64–348.92 μg/kg). Temporal decreasing trends were observed for DDTs, HCHs, PBDEs, PCDD&Fs, and PFOA, with no significant change for other POPs. Meanwhile, the estimated daily intake for adults were 75.2 ± 43.6 ng/kg/day for DDTs, 123 ± 87 ng/kg/day for HCHs, 0.37 ± 0.17 pg TEQ/kg/day for PCDD&Fs, 17.8 ± 9.5 ng/kg/day for PCBs, 3.3 ± 1.8 ng/kg/day for PBDEs, 3.6 ± 1.9 ng/kg/day for PFOA, 3.3 ± 2.0 ng/kg/day for PFOS, and 2.5 ± 1.6 μg/kg/day for SCCPs. Furthermore, non-carcinogenic risks were the highest for PCBs (0.89) and PCDD&Fs (0.53), followed by PFOA (0.18), PFOS (0.17), HCHs (0.062), SCCPs (0.025), DDTs (0.0075), and PBDEs (0.00047). These findings illustrated that exposure to POPs declined due to the control policies implemented in China, while the cumulative risk of POPs was still higher than 1, indicating continuous efforts are required to mitigate associated contamination.

A paradoxical impact of high rates of production and consumption of antibiotics is their widespread release in the environment. Consequently, low concentrations of antibiotics and their byproducts have been routinely identified from various environmental settings especially from aquatic environments. However, the impact of such low concentrations of antibiotics on the exposed host especially in early life remains poorly understood. We exposed zebrafish to two different environmental concentrations of oxytetracycline and sulfamethoxazole, from larval stage to adulthood (∼120 days) and characterized their impact on the taxonomic diversity, antibiotic resistance genes, and metabolic pathways of the gut microbiome using metagenomic shotgun sequencing and analysis. Long term exposure of environmental concentrations of oxytetracycline and sulfamethoxazole significantly impacted the taxonomic composition and metabolic pathways of zebrafish gut microbiome. The antibiotic exposed samples exhibited significant enrichment of multiple flavobacterial species, including Flavobacterium sp. F52, Flavobacterium johnsoniae and Flavobacterium sp. Fl, which are well known pathogenic bacteria. The relative abundance of antibiotic resistance genes, especially several tetratcycline and sulfonamide resistance genes were significantly higher in the exposed samples and showed a linear correlation with the antibiotic concentrations. Furthermore, several metabolic pathways, including folate biosynthesis, oxidative phosphorylation, and biotin metabolism pathways, showed significant enrichment in the antibiotic exposed samples. Collectively, our results suggest that early life exposure of the environmental concentrations of antibiotics can increase the abundance of unfavorable bacteria, antibiotic resistance genes and associated pathways in the gut microbiome of zebrafish.

Forest-stream ecosystems are widespread and biodiverse terrestrial landscapes with physical and social connections to downstream human activities. After radiocesium is introduced into these ecosystems, various material flows cause its accumulation or dispersal. We review studies conducted in the decade after the Fukushima nuclear accident to clarify the mechanisms of radiocesium transfer within ecosystems and to downstream areas through biological, hydrological, and geomorphological processes. After its introduction, radiocesium is heavily deposited in the organic soil layer, leading to persistent circulation due to biological activities in soils. Some radiocesium in soils, litter, and organisms is transported to stream ecosystems, forming contamination spots in depositional habitats. While reservoir dams function as effective traps, radiocesium leaching from sediments is a continual phenomenon causing re-contamination downstream. Integration of data regarding radiocesium dynamics and contamination sites, as proposed here, is essential for contamination management in societies depending on nuclear power to address the climate crisis.

The assessment of the distribution and composition of microlitter in the sea is a great challenge. Biological indicators can be an irreplaceable tool since they measure microlitter levels in their environments in a way that is virtually impossible to replicate by direct physical measurements. Furthermore, trends can provide policymakers with statistically robust analysis. We looked into the capacity of multiple fish species to describe the distribution and composition of microlitter vertically across different compartments of the water column. A total of 502 individuals from six selected species (Scomber scombrus, Oblada melanura, Spicara smaris, Boops boops, Merluccius merluccius and Mullus barbatus) were collected on the western side of Sardinia island and allocated to three compartments: surface, mid-water and bottom. The species of the surface exhibited a higher frequency of occurrence (41.89%) of microlitter ingestion, compared to those of the mid-water and bottom (19.60%; 22.58%). A significant difference in the average number of ingested microlitter was found between the surface and the bottom compartment. All the microlitter fragments found were analysed through Fourier Transform Infrared Spectroscopy (FTIR). The comparison of the expected buoyancies of the polymers identified puth faith in the allocation of the species to the respective compartments. Therefore, considering the Marine Strategy Framework Directive objective, this approach could be useful in assessing microlitter distribution and composition vertically across the water column.

Microplastic pollution is widely recognised as a global issue, posing risks to natural ecosystems and human health. The combination of rapid industrial and urban development and relatively limited environmental regulation in many tropical countries may increase the amount of microplastic entering rivers, but basic data on contamination levels are lacking. This is especially the case in tropical South East Asian countries. In this paper, the abundance, composition and spatio-temporal variation of microplastic in the Langat River, Malaysia, were assessed, and the relationship between microplastic concentration and river discharge was investigated. Water samples were collected over a 12-month period from 8 sampling sites on the Langat, extending from forested to heavily urbanised and industrial areas. All 508 water samples collected over this period contained microplastic; mean concentration across all sites and times was 4.39 particles/L but extended up to 90.00 particles/L in some urban tributaries. Most microplastics were secondary in origin, and dominated by fibres. Microplastic counts correlated directly with river discharge, and counts increased and decreased in response to changes in flow. A time-integrated assessment of the microplastic load conveyed by the Langat suggested that the river is typically (50 % of the time) delivering around 5 billion particles per day to the ocean. The positive correlation between the concentration of microplastics and suspended sediments in the Langat suggested that continuously logging turbidity sensors could be used to provide better estimates of microplastic loads and improve assessment of human and ecological health risks.

An experimentally induced three-dimensional petroleum seepage flume was used to investigate its migration in heterogeneous soil layers and a method for monitoring resistivity was adopted, under conditions of fluctuating water levels and rainfall. The corresponding mechanisms were then analyzed based on the resistivity characteristics and combined with three-dimensional inversion images. Finally, physical and chemical property analysis was conducted to verify the results of resistivity monitoring. The results demonstrated that: (1) In the process of natural oil leakage, the variation of soil resistivity presents a concave shape in the resistivity profile. Thus, oil migration exhibited the following patterns. At first, circular migration front was dominant in a vertical direction. Subsequently, after vertical migration was impeded, lateral migration was dominant. As the crude oil gradually accumulated, the migration front broke through the limitation of lithologic interface and continued vertically. (2) By comparing the two resistivity monitoring methods, namely the Wenner and Pole-pole methods, it was demonstrated that the inversion resistivity measured by Wenner method was closer to the true resistivity, and the resistivity variations were more distinguishable. (3) The resistivity inversion profile demonstrated that the low resistivity anomaly of the crude oil leakage area was related to the low water content of the soil layer in the test area. (4) Fluctuations in water level increased the diffusion range of crude oil beyond the original pollution source area, especially horizontally. (5) Percolation of rainfall caused the water level to rise, and the crude oil was evenly distributed in the soil layers above the capillary zone. (6) Through sample analysis and verification, it was demonstrated that the resistivity method can accurately and intuitively present the characteristics of crude oil migration. These results provide theoretical support for the rapid determination of the migration range and characteristics of crude oil in heterogeneous soil layers.

Crop residue open burning has substantial negative effects on air quality, human health, and climate change, and accurate and timely estimates of its air pollutant emissions are essential. Open burning proportion (OBP) is the key parameter in estimating the emission from the crop residue open burning by bottom-up method. However, the OBP is mainly obtained by field investigation, which consumes much time, manpower and financial resources, leading to the OBP data deficient seriously. In this study, the significant logarithmic relations were found between OBP and fire radiative energy (FRE), and then the FRE-based OBP estimation models were developed for different regions of China. The comparison between the FRE-based OBP and the field-investigated OBP illustrated the reliability of the developed models (r = 0.71, NMB = −8% and NME = 25%). The OBPs of different municipalities/provinces in mainland China from 2003 to 2018 were further calculated. The results showed that the estimated OBP variation exhibited fluctuating upward trend with annual mean growth rate of 3.7% from 2003 to 2014, while dramatically decreased with annual mean reduction rate of 5.9% from 2014 to 2018. The estimation accuracy of emission from open biomass burning can also be can be significantly improved by basing on the year-specific OBP, compared with the calculation based on fixed OBP. The annual PM₂.₅ emissions would decrease 4.5%–25.9% and increase 6.6%–30.7% in the scenarios of a fixed OBP during 2003–2014 and 2014–2018, respectively. The developed models complemented the severely missing OBP data of mainland China for the first time. By combining the advantages of bottom-up approach and FRE method, the proposed FRE-based models can avoid their disadvantages, and can help to get more accurately and timely emissions from crop residue open burning.

Farmland birds are declining across Europe and North America and the research of factors behind is the subject of extensive researches. Agricultural intensification is now recognized as a major factor governing the loss of biodiversity with strong evidence that pesticides induced direct bird mortality at a high dose. However, less attention has been given to the long-term effects of chronic exposure to low dose of pesticides. Here, we used an experimental procedure in which grey partridges were fed with untreated grains obtained from either organic (no pesticide) or conventional agriculture (with pesticide) for 26 weeks, thus strictly mimicking wild birds foraging on fields. We then examined a suite of life-history traits (ecophysiological and behavioural) that may ultimately, influence population dynamics. We show for the first time that ingesting low pesticide doses over a long period has long-term consequences on several major physiological pathways without inducing differential mortality. Compared to control partridges, birds exposed to chronic doses i) had less developed carotenoid-based ornaments due to lower concentrations of plasmatic carotenoids, ii) had higher activated immune system, iii) showed signs of physiological stress inducing a higher intestinal parasitic load, iv) had higher behavioural activity and body condition and v) showed lower breeding investment. Our results are consistent with a hormetic effect, in which exposure to a low dose of a chemical agent may induce a positive response, but our results also indicate that breeding adults may show impaired fitness traits bearing population consequences through reduced breeding investment or productivity. Given the current scale of use of pesticides in agrosystems, we suggest that such shifts in life-history traits may have a negative long-term impact on wild bird populations across agrosystems. We stress that long-term effects should no longer be ignored in pesticide risk assessment, where currently, only short-term effects are taken into account.