Wastewater irrigation may introduce antibiotic residues in the soil-plant systems. This study aimed to investigate the uptake of tetracyclines by spinach and collard greens and assess associated ecological and human health risks. Synthetic wastewater spiked with 1 ppm and 10 ppm of oxytetracycline, doxycycline, and tetracycline was used to grow vegetables in a greenhouse pot experiment. The uptake and accumulation of the tetracyclines were low and residual concentrations in the soil were negligible. All the tetracyclines were detected at concentrations ranging from 1.68 to 51.41 μg/g (spinach) and 1.94–30.95 μg/g (collard greens). The accumulation rate was in a dose-response scenario with a bioconcentration factor of 6.34 mL/kg (spinach) and 2.64 mL/kg (collard greens). Oxytetracycline had the highest accumulation in leaves, followed by doxycycline and tetracycline, and the residual concentrations followed the same order. The highest residual concentration was in soils receiving 10 ppm oxytetracycline. Residual concentrations in the soil were lower than accumulated levels and exerted negligible ecological risks. Tetracyclines accumulation in spinach significantly differed between the vegetables demonstrating a subspecies difference in uptake and accumulation. Ecological risk quotient (RQ) and human health risk quotient (HQ) were below thresholds that would exert toxicity and resistance selection impacts. Although RQs and HQs are low (<0.1), this study shows that the vegetables accumulate tetracyclines from irrigation water, posing plausible human health risks to allergic individuals. Similarly, the ecological risks cannot be ignored because the synergistic and antagonistic effects of sublethal concentrations can perturb ecosystem processes.

Groundwater nitrate (NO₃⁻) pollution is a worldwide environmental problem. Therefore, identification and partitioning of its potential sources are of great importance for effective control of groundwater quality. The current study was carried out to identify the potential sources of groundwater NO₃⁻ pollution and determine their apportionment in different land use/land cover (LULC) types in a traditional agricultural area, Weining Plain, in Northwest China. Multiple hydrochemical indices, as well as dual NO₃⁻ isotopes (δ¹⁵N–NO₃ and δ¹⁸O–NO₃), were used to investigate the groundwater quality and its influencing factors. LULC patterns of the study area were first determined by interpreting remote sensing image data collected from the Sentinel-2 satellite, then the Bayesian stable isotope mixing model (MixSIAR) was used to estimate proportional contributions of the potential sources to groundwater NO₃⁻ concentrations. Groundwater quality in the study area was influenced by both natural and anthropogenic factors, with anthropological impact being more important. The results of LULC revealed that the irrigated land is the dominant LULC type in the plain, covering an area of 576.6 km² (57.18% of the total surface study area of the plain). On the other hand, the results of the NO₃⁻ isotopes suggested that manure and sewage (M&S), as well as soil nitrogen (SN), were the major contributors to groundwater NO₃⁻. Moreover, the results obtained from the MixSIAR model showed that the mean proportional contributions of M&S to groundwater NO₃⁻ were 55.5, 43.4, 21.4, and 78.7% in the forest, irrigated, paddy, and urban lands, respectively. While SN showed mean proportional contributions of 29.9, 43.4, 61.5, and 12.7% in the forest, irrigated, paddy, and urban lands, respectively. The current study provides valuable information for local authorities to support sustainable groundwater management in the study region.

The influence of regional transport on aerosol pollution has been explored in previous studies based on numerical simulation or surface observation. Nevertheless, owing to inhomogeneous vertical distribution of air pollutants, vertical observations should be conducted for a comprehensive understanding of regional transport. Here we obtained the vertical profiles of aerosol and its precursors using ground-based multi-axis differential optical absorption spectroscopy (MAX-DOAS) at the Nancheng site in suburban Beijing on the southwest transport pathway of the Beijing-Tianjin-Hebei (BTH) region, China, and then estimated the vertical profiles of transport fluxes in the southwest-northeast direction. The maximum net transport fluxes per unit cross-sectional area, calculated as pollutant concentration multiply by wind speed, of aerosol extinction coefficient (AEC), NO₂, SO₂ and HCHO were 0.98 km⁻¹ m s⁻¹, 24, 14 and 8.0 μg m⁻² s⁻¹ from southwest to northeast, which occurred in the 200–300 m, 100–200 m, 500–600 m and 500–600 m layers, respectively, due to much higher pollutant concentrations during southwest transport than during northeast transport in these layers. The average net column transport fluxes were 1200 km⁻¹ m² s⁻¹, 38, 26 and 15 mg m⁻¹ s⁻¹ from southwest to northeast for AEC, NO₂, SO₂ and HCHO, respectively, in which the fluxes in the surface layer (0–100 m) accounted for only 2.3%–4.2%. Evaluation only based on surface observation would underestimate the influence of the transport from southwest cities to Beijing. Northeast or weak southwest transports dominated in clean conditions with PM₂.₅ <75 μg m⁻³ and intense southwest transport dominated in polluted conditions with PM₂.₅ >75 μg m⁻³. Southwest transport through the middle boundary layer was a trigger factor for aerosol pollution events in urban Beijing, because it not only directly bringing air pollutants, but also induced an inverse structure of aerosols, which resulted in stronger atmospheric stability and aggravated air pollution in urban Beijing.

Although it is a probable human carcinogen, propylene oxide is widely applied in industry and daily life. However, data on neurodevelopmental effects of propylene oxide exposure among children are extremely limited. We aimed to determine the urinary concentrations of propylene oxide metabolite among school-aged children and evaluate the potential association of propylene oxide exposure with risk of dyslexia. A total of 355 dyslexic children and 390 controls were recruited from three cities (Jining, Wuhan, and Hangzhou) in China, between 2017 and 2020. Urinary N-acetyl-S-(2-hydroxypropyl)-L-cysteine (i.e., 2-hydroxypropyl mercapturic acid; 2-HPMA) was measured as the biomarker of propylene oxide exposure. The detection frequency of 2-HPMA was 100%. After adjusting for potential confounders, the odds ratio (OR) for dyslexia per 2-fold increase in urinary 2-HPMA was 1.19 [95% confidence interval (95% CI): 1.01, 1.40, P = 0.042]. Compared with the lowest quartile of urinary 2-HPMA concentrations, children with the highest quartile of 2-HPMA had a 1.63-fold (95% CI: 1.03, 2.56, P = 0.036) significantly increased risk of dyslexia, with a dose-response relationship (P-trend = 0.047). This study provides epidemiological data on the potential association between propylene oxide exposure and the risk of dyslexia in children. Further studies are warranted to confirm the findings and reveal the underlying biological mechanisms.

The impact of land use type on the content of potentially toxic elements (PTEs) in the soils of the Qinghai-Tibet Plateau (QTP) and the associated ecological and human health risks has drawn great attention. Consequently, in this study, top- and subsurface soil samples were collected from areas with four different land uses (i.e., cropland, forest, grassland, and developed area) and the total contents of Cr, Cd, Cu, Pb and Zn were determined. Geostatistical analysis, self-organizing map (SOM), and positive matrix factorization (PMF), ecological risk assessment (ERA) and human health risk assessment (HRA) were applied and used to classify and identify the contamination sources and assess the potential risk. Partial least squares path modeling (PLS-PM) was applied to clarify the relationship of land use with PTE contents and risk. The PTE contents in all topsoil samples surpassed the respective background concentrations of China and corresponding subsurface concentrations. However, the ecological risk of all soil samples remained at a moderate or considerable level across the four land use types. Developed area and cropland showed a higher ecological risk than the other two land use types. Industrial discharges (32.8%), agricultural inputs (22.6%), natural sources (23.7%), and traffic emissions (20.9%) were the primary PTE sources in the tested soils, which indicate that anthropogenic activities have significantly affected soil PTE contents to a greater extent than other sources. Industrial discharge was the most prominent source of non-carcinogenic health risk, contributing 37.7% for adults and 35.2% for children of the total risk. The results of PLS-PM revealed that land use change associated with intensive human activities such as industrial activities and agricultural practices distinctly affected the PTE contents in soils of the Qinghai-Tibet Plateau.

Carbonaceous aerosols pose significant climatic impact, however, their sources and respective contribution to light absorption vary and remain poorly understood. In this work, filter-based PM₂.₅ samples were collected in winter of 2021 at three urban sites in Yibin, a fast-growing city in the south of Sichuan Basin, China. The composition characteristics of PM₂.₅, light absorption and source of carbonaceous aerosol were analyzed. The city-wide average concentration of PM₂.₅ was 87.4 ± 31.0 μg/m³ in winter. Carbonaceous aerosol was the most abundant species, accounting for 42.5% of the total PM₂.₅. Source apportionment results showed that vehicular emission was the main source of PM₂.₅ during winter, contributing 34.6% to PM₂.₅. The light absorption of black carbon (BC) and brown carbon (BrC) were derived from a simplified two-component model. We apportioned the light absorption of carbonaceous aerosols to BC and BrC using the Least Squares Linear Regression with optimal angstrom absorption exponent of BC (AAEBC). The average absorption of BC and BrC at 405 nm were 51.6 ± 21.5 Mm⁻¹ and 17.7 ± 8.0 Mm⁻¹, respectively, with mean AAEBC = 0.82 ± 0.02. The contribution of BrC to the absorption of carbonaceous reached 26.1% at 405 nm. Based on the PM₂.₅ source apportionment and the mass absorption cross-section (MAC) value of BrC at 405 nm, vehicle emission was found to be the dominant source of BrC in winter, contributing up to 56.4%. Therefore, vehicle emissions mitigation should be the primary and an effective way to improve atmospheric visibility in this fast-developing city.

Exposure to electronic and electrical waste (e-waste) has been related to a few adverse health effects. In this study, sediment samples from an e-waste recycling town in China were collected, and aryl hydrocarbon receptor (AhR) agonists in the samples were identified using an effect-directed analysis (EDA) strategy. The CBG2.8D cell line reporter gene bioassay was used as a toxicity test, while suspect screening against chemical databases was performed for potential AhR agonist identification where both gas chromatography- and liquid chromatography-high resolution mass spectrometry analyses were run. When the original sample extract showed high AhR-mediated activity, sample fractionation was performed, and fractions exhibiting high bioactivity were chemically analyzed again to reveal the corresponding AhR agonists. In total, 23 AhR agonists were identified, including 14 commonly known ones and 9 new ones. Benzo [k]fluoranthene and 6-nitrochrysene were the dominant AhR agonists, covering 16–71% and 2.7–12%, respectively, of the AhR activation effects measured in the parent extracts. The newly identified AhR-active chemicals combined explained 0.13–0.20% of the parent extracts’ effects, with 7,12-dimethylbenz [a]anthracene and 8,9,11-trimethylbenz [a]anthracene being the major contributors. A diagnostic isomer ratio analysis of polycyclic aromatic hydrocarbons suggested that the major source of AhR agonists identified in these e-waste related sediment samples were probably petroleum product combustion and biomass combustion. In the future, for a more comprehensive AhR agonist investigation, in-house chemical synthesis and purification, and, when necessary, a secondary sample fractionation, would be beneficial.

Although biomass fuel has always been regarded as a source of sustainable energy, it potentially emits polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs). This study investigated PCDD/F emissions from industrial boilers fired with three types of biomass fuel (i.e., bagasse, coffee residue, and biomass pellets) via stack sampling and laboratory analysis. The measured mass concentrations of PCDD/Fs varied among the boilers from 0.0491 to 12.7 ng Nm⁻³ (11% O₂), with the calculated average international toxic equivalent quantity (I-TEQ) from 0.00195 to 1.71 ng I-TEQ Nm⁻³ (11% O₂). Some of them were beyond the limit value for municipal waste incineration. 2,3,4,7,8-PeCDF could be used as a good indicator of dioxin-induced toxicity of stack flue gases from biomass-fired boilers. The PCDFs/PCDDs ratios were more than 1, likely indicating the formation of dioxins in the boilers favored by de novo synthesis. The emission factor (EF) of total PCDD/Fs averaged 5.35 ng I-TEQ kg⁻¹ air-dry biomass (equivalent to 39.0 ng kg⁻¹ air-dry biomass). Specifically, the mean EF was 6.94 ng I-TEQ kg⁻¹ (52.6 ng kg⁻¹) for biomass-pellet-fired boiler, 11.8 ng I-TEQ kg⁻¹ (74.6 ng kg⁻¹) for coffee-residue -fired boiler, and 0.0277 ng I-TEQ kg⁻¹ (0.489 ng kg⁻¹) for bagasse-fired boilers. The annual PCDD/F emission was estimated to be 208 g I-TEQ in 2020 in China, accounting for approximately 2% of the total national annual emission of PCDD/Fs. The results can be used to develop PCDD/Fs emission inventories and offer valuable insights to authorities regarding utilizing biomass in industry in the future.

Because of a shortage of water resources, sewage irrigation has become a popular management tool for farmland soil in arid areas of China; however, this has led to the accumulation of polycyclic aromatic hydrocarbons (PAHs) in soil. Soil is an important component of ecosystems, and nitrogen is an important nutrient required for plant growth. Nitrogen input can alter the physical, chemical, and biological processes in soil and thus lead to changes in soil organic matter and organic pollutants. However, whether these changes affect the accumulation of PAHs and whether such accumulation differs in the low-density fraction (LF) and high-density fraction (HF) of soil remains unclear. In this study, the response of PAHs in soil to nitrogen input (0, 100, 200, and 300 kg N ha⁻¹ yr⁻¹, respectively), including differences in LF and HF, were investigated through field experiments in a typical sewage-irrigated area. The results showed that nitrogen input could increase the concentrations of PAHs in soil from (7.6 ± 1.1) × 10³ to (10.4 ± 0.6) × 10³ μg kg⁻¹ and lead to striking differences between the LF ((5.06 ± 0.75) × 10³ to (1.89 ± 0.18) × 10³ μg kg⁻¹) and HF ((2.54 ± 0.36) × 10³ to (8.54 ± 0.44) × 10³ μg kg⁻¹). Given the significant increase in global nitrogen input, our findings have implications for the optimization and management of agricultural activities in sewage irrigation areas, such as soil investigation before fertilization, the use of soil improvers, and the improvement of soil planting measures.