Paraquat (PQ) is one of the most widely used herbicides in the world due to its excellent weed control effects. Accumulating evidence has revealed that long-term exposure to PQ can significantly increase the risk of Parkinson’s disease (PD). However, the underlying molecular mechanisms are yet to be fully understood. Hence, we investigated the potential role of reactive oxygen species (ROS) and dynamin-related protein 1 (DRP1) in PQ-induced mitophagy, aiming to elaborate on possible molecular mechanisms involved in PQ-triggered neurotoxicity. Our results showed that ROS were increased, mitochondrial membrane potential was decreased at 100, 200, and 300 μM PQ concentrations, and autophagy pathways were activated at a concentration of 100 μM in neuronal cells. In addition, excessive mitophagy was observed in neurons exposed to 300 μM PQ for 24 h. Then, ROS-mediated mitochondrial fission was found to contribute to PQ-induced excessive mitophagy. Moreover, all aforementioned changes were significantly ameliorated by mdivi-1. Thus, our findings provide a novel neurotoxic mechanism and reveal the DRP1-mitochondrial fission pathway as a potential target for treatments of PQ-induced excessive mitophagy, serving as an alternative target for the prevention and treatment of Parkinson’s disease. Because harmful substances are transmitted and enriched in the food chain, the toxic effect of environmental paraquat is nonnegligible, and more investigations are needed.

High concentrations of ground-level ozone affect human health, plants, and animals. Reducing ozone pollution in rural regions, where local emissions are already low, poses challenge. We use meteorological back-trajectories, air quality model sensitivity analysis, and satellite remote sensing data to investigate the ozone sources in Yuma, Arizona and find strong international influences from Northern Mexico on 12 out of 16 ozone exceedance days. We find that such exceedances could not be mitigated by reducing emissions in Arizona; complete removal of state emissions would reduce the maximum daily 8-h average (MDA8) ozone in Yuma by only 0.7% on exceeding days. In contrast, emissions in Mexico are estimated to contribute to 11% of the ozone during these exceedances, and their reduction would reduce MDA8 ozone in Yuma to below the standard. Using satellite-based remote sensing measurements, we find that emissions of nitrogen oxides (NOₓ, a key photochemical precursor of ozone) increase slightly in Mexico from 2005 to 2016, opposite to decreases shown in the bottom-up inventory. In comparison, a decrease of NOₓ emissions in the US and meteorological factors lead to an overall of summer mean and annual MDA8 ozone in Yuma (by ∼1–4% and ∼3%, respectively). Analysis of meteorological back-trajectories also shows similar transboundary transport of ozone at the US-Mexico border in California and New Mexico, where strong influences from Northern Mexico coincide with 11 out of 17 and 6 out of 8 ozone exceedances. 2020 is the final year of the U.S.-Mexico Border 2020 Program, which aimed to reduce pollution at border regions of the US and Mexico. Our results indicate the importance of sustaining a substantial cooperative program to improve air quality at the border area.

Nitrate leaching caused by overusing or misusing nitrogen (N) fertilizers in field vegetable cropping systems in China is a leading contributor to nitrate contamination of groundwater. Identification of the critical fertilizer N input rate could support management decisions that maintain yields while reducing the impact of nitrate leaching on groundwater. A four-season field experiment involving six N treatments (0, 60, 120, 180, 240, and 300 kg N ha⁻¹) was undertaken to investigate the impacts of various N rates on N use efficiency (NUE), seasonal nitrate leaching loss (SNLL), nitrate residue (NR), and radish yield, and to identify the critical N fertilizer rate for both optimum yield and minimum nitrate leaching loss in a field vegetable (radish, Raphanus sativus L.) cropping system in northern China. The results showed that radish yield enhanced quadratically and NUE reduced linearly with increasing N addition, while the NR and SNLL increased exponentially. The yield did not increase markedly when N fertilization exceeded 180 kg N ha⁻¹. SNLL and nitrate concentrations in the leachate averaged 11.5–71.5 kg N ha⁻¹ and 5.1–35.6 mg N L⁻¹, respectively, under N rates of 60–300 kg N ha⁻¹. The results showed that N fertilizer rate ranging from 180 to 196 kg N ha⁻¹ resulted in high yields and low nitrate leaching losses. Compared with those in response to the N fertilizer amount applied by local farmers, the NUE, NR, and SNLL in response to the N fertilizer amount identified in this study increased, decreased by 30.9%–35.0%, and decreased by 49.9%–55.7%, respectively, without any yield loss. Thus, a critical N fertilizer rate ranging from 180 to 196 kg N ha⁻¹ is recommended to obtain optimum yields with minimal environmental risks in radish fields in northern China.

To prevent spreads of Coronavirus disease-2019 (COVID-19), China adopted the lockdown measures in late January 2020, providing a platform to study the response of air quality and atmospheric chemical and physical properties to strict reduced emissions. In this study, the continuous measurements of aerosol light absorption were conducted in Nanjing, east China, from January 3 to March 31, 2020. Our results showed that the contribution of black carbon (BC) to light absorption at the different wavelengths was more than 75% and the rest light absorption was contributed by brown carbon (BrC), which was mainly originated from primary emissions. Secondary BrC absorption, which was mainly produced by photochemical oxidation, constituted a minor fraction (2–7%) of the total absorption. Compared with the sampling in the pre-lockdown, the significant decreases of BC (43%) and secondary BrC absorption (31%) were found during the lockdown period, resulting in a substantial decrease of solar energy absorbance by 36% on a local scale. The control measures also changed the diurnal variations of light absorption. Due to the reduced emissions, the relative fraction of fossil fuel to BC also dropped from 78% in the pre-lockdown to 71% in the lockdown. The concentrations of BC, PM₂.₅ and NO₂ decreased 1.1 μg m⁻³, 33 μg m⁻³ and 9.1 ppb whereas O₃ concentration increased 9.0 ppb during the COVID-19 lockdown period. The decreased concentrations of BC, PM₂.₅ and NO₂ were mainly contributed by both emission reduction (51–64%) and meteorological conditions (36–49%). Our results highlighted that the balance of control measures in alleviation of particulate matter (PM) and O₃ pollution, and meteorology should be seriously considered for improvement of air quality in this urban city of China.

Transition metals (TMs) (e.g. copper (Cu) and iron (Fe)) and certain organic compounds are known active constituents causing oxidative potential (OP) by inhaled ambient fine particulate matter (PM₂.₅) in lung fluid. Humic-like substances (HULIS), isolated from atmospheric PM₂.₅, are largely metal-free and contain mixtures of organics that are capable of complexing TMs. TMs and HULIS co-exist in the water-extractable part of PM₂.₅. In this work, we used a solid phase extraction procedure to isolate the water-soluble TMs in the hydrophilic fraction (HPI) and HULIS in the hydrophobic fraction (HPO) and carried out this isolation procedure to a set of 32 real-world PM₂.₅ samples collected in Beijing and Hong Kong, China. We quantified two OP endpoints, namely hydroxyl radical formation (denoted as OP•OH) and ascorbic acid depletion (denoted as OPAA), by the two fractions separately and combined, as well as by the bulk water-soluble aerosols. OP•OH and OPAA were well-correlated in both separate fractions and their combined mixtures or bulk water-soluble aerosols. OP by HPI far exceeded that by HPO. On a per unit PM₂.₅ mass basis, the Hong Kong samples on average had a higher OPAA and OP•OH than the Beijing samples due to more water-soluble Cu. For HPI, Cu was a dominant OP•OH and OPAA contributor (>80%), although water-soluble Fe was present at a concentration approximately one order of magnitude higher. Suppression effects on OP•OH were observed through comparing the OP of the bulk water-soluble aerosol with that of HPI. Our work reveals the importance of monitoring PM₂.₅ chemical compositions (especially water-soluble redox active metals). Furthermore, we demonstrate the need to consider metal-organic interactions when evaluating the aggregate OP by PM₂.₅ from individual components or apportioning OP by PM₂.₅ to specific chemical components.

Microplastic pollution is emerging as a global environmental issue, and its potential for transferring hazardous chemicals to aquatic organisms is gaining attention. Studies have investigated the transfer of chemicals, mainly sorbed chemicals, through ingestion of microplastics by organisms, but limited information is available regarding chemical additives and uptake via the aqueous route through plastic leaching. In this study, we compared two bioaccumulation pathways of the additive hexabromocyclododecane (HBCD) by exposing mussels (Mytilus galloprovincialis) to two different sizes of expanded polystyrene (EPS): inedible size (4.2–5.5 mm) for leachate uptake and edible size (20–770 μm) for particle ingestion and leachate uptake. Over 10 days, the HBCD concentration increased significantly in mussels in the EPS exposure groups, indicating that EPS microplastic acts as a source of HBCD to mussels. The concentration and isomeric profiles of HBCD in mussels show that uptake through the aqueous phase is a more significant pathway for bioaccumulation of HBCD from EPS to mussels than particle ingestion. HBCD levels measured in EPS, leachate and exposed mussels from this study are environmentally relevant concentration. The fate and effects of chemical additives leached from plastic debris in ecosystem requires further investigation, as it may affect numerous environments and organisms through the aqueous phase.

Tributyltin (TBT) is a widely used organotin compound around the world and was frequently detected in surface waters, which would pose risk to aquatic organisms. However, the mechanisms of TBT-induced toxicity is not full clear. The present study investigated the effects of the tributyltin (TBT) on the blood parameters, immune responses and thyroid hormone system in zebrafish. Fish were exposed to sublethal concentrations of TBT (10 ng/L, 100 ng/L and 300 ng/L) for 6 weeks. The effects of long-term exposure to TBT on blood parameters (NH3, ammonia; GLU, glucose; TP, total proteins; CK, creatine kinase; ALT, alanine aminotransferase; AST, aspartate aminotransferase), immune responses (Lys, lysozyme; IgM, immunoglobulin M) and some indexes related thyroid hormone system (T3, 3,5,3′-triiodothyronine; T4, thyroxine) were measured in zebrafish, as well as the expression of genes related to immune responses and thyroid hormone system. Based on the results, the physiological-biochemical responses was significantly enhanced with an increase in TBT concentration, reflected by the abnormal blood indices, dysregulation of endocrine system and immunotoxicity in zebrafish under TBT stress. The present study greatly extends our understanding of adverse effects of TBT on aquatic organisms.

Private wells in Ireland and elsewhere have been shown to be prone to microbial contamination with the main suspected sources being practices associated with agriculture and domestic wastewater treatment systems (DWWTS). While the microbial quality of private well water is commonly assessed using faecal indicator bacteria, such as Escherichia coli, such organisms are not usually source-specific, and hence cannot definitively conclude the exact origin of the contamination. This research assessed a range of different chemical contamination fingerprinting techniques (ionic ratios, artificial sweeteners, caffeine, fluorescent whitening compounds, faecal sterol profiles and pharmaceuticals) as to their use to apportion contamination of private wells between human wastewater and animal husbandry wastes in rural areas of Ireland. A one-off sampling and analysis campaign of 212 private wells found that 15% were contaminated with E. coli. More extensive monitoring of 24 selected wells found 58% to be contaminated with E. coli on at least one occasion over a 14-month period. The application of fingerprinting techniques to these monitored wells found that the use of chloride/bromide and potassium/sodium ratios is a useful low-cost fingerprinting technique capable of identifying impacts from human wastewater and organic agricultural contamination, respectively. The artificial sweetener acesulfame was detected on several occasions in a number of monitored wells, indicating its conservative nature and potential use as a fingerprinting technique for human wastewater. However, neither fluorescent whitening compounds nor caffeine were detected in any wells, and faecal sterol profiles proved inconclusive, suggesting limited suitability for the conditions investigated.

Crude oil pollution is a global environmental concern since it persists in the environment longer than most conventional carbon sources. In December 2014, the hyper-arid Evrona Nature Reserve, Israel, experienced large-scale contamination when crude oil spilled. The overarching goal of the study was to investigate the possible changes, caused by an accidental crude oil spill, in the leaf reflectance and biochemical composition of four natural habitat desert shrubs. The specific objectives were (1) to monitor the biochemical properties of dominant shrub species in the polluted and control areas; (2) to study the long-term consequences of the contamination; (3) to provide information that will assist in planning rehabilitation actions; and (4) to explore the feasibility of vegetation indices (VIs), along with the machine learning (ML) technique, for detecting stressed shrubs based on the full spectral range. Four measurement campaigns were conducted in 2018 and 2019. Along with the various stress indicators, field spectral measurements were performed in the range of 350–2500 nm. A regression analysis to examine the relation of leaf reflectance to biochemical contents was carried out, to reveal the relevant wavelengths in which polluted and control plants differ. Vegetation indices applied in previous studies were found to be less sensitive for indirect detection of long-term oil contamination. A novel spectral index, based on indicative spectral bands, named the “normalized blue-green stress index” (NBGSI), was established. The NBGSI distinguished significantly between shrubs located in the polluted and in the control areas. The NBGSI showed a strong linear correlation with pheophytin a. Machine learning classification algorithms obtained high overall prediction accuracy in distinguishing between shrubs located in the oil-polluted and the control sites, indicating internal component differences. The findings of this study demonstrate the efficacy of indirect and non-destructive spectral tools for detecting and monitoring oil pollution stress in shrubs.

In this work, valorisation pathways of brewers’ spent grains (BSG) towards biofuels production under the biorefinery concept were studied utilizing experimental data that provide a common base for straightforward comparison. The dehydration and the recovery of used oil, bioethanol and biogas from BSG were studied. The process units involved were thoroughly investigated and optimized. The oil extraction efficiency reached up to 70% using solid-liquid extraction process with hexane as solvent. The optimal ethanol yield achieved was 45% after the application of acid pretreatment, enzymatic hydrolysis with CellicCTec2 and fermentation with S. Cerevisiae. As far as biogas potential is concerned, the raw BSG, defatted BSG and stillage presented values equal to 379 ± 19, 235 ± 21 and 168 ± 39 mL biogas/g for respectively. Through the combination of the proposed schemes, three biorefinery scenarios were set up able to produce biodiesel, bioethanol and/or biogas. Material flow diagrams were set up in order to assess these schemes. Given that BSG could ensure ‘green’ energy production in the range of 4.5–7.0 million MJ/y if the European BSG potential is fully valorised, BSG could substantially contribute to the biofuel energy strategy.