This study presents a comprehensive analysis of organic carbon (OC), elemental carbon (EC), and particularly the light absorption characteristics of EC and water-soluble brown carbon (WS–BrC) in total suspended particles in the Kathmandu Valley from April 2013 to January 2018. The mean OC, EC, and water-soluble organic carbon (WSOC) concentrations were 34.8 ± 27.1, 9.9 ± 5.8, and 17.4 ± 12.5 μg m⁻³, respectively. A clear seasonal variation was observed for all carbonaceous components with higher concentrations occurring during colder months and lower concentrations in the monsoon season. The relatively low OC/EC ratio (3.6 ± 2.0) indicates fossil fuel combustion as the primary source of carbonaceous components. The optical attenuation (ATN) at 632 nm was significantly connected with EC loading (ECS) below 15 μg cm⁻² but ceased as ECS increased, reflecting the increased influence of the shadowing effect. The derived average mass absorption cross-section of EC (MACEC) (7.0 ± 4.2 m² g⁻¹) is comparable to that of freshly emitted EC particles, further attesting that EC was mainly produced from local sources with minimal atmospheric aging processes. Relatively intensive coating with organic aerosols and/or salts (e.g., sulfate, nitrate) was probably the reason for the slightly higher MACEC during the monsoon season, whereas increased biomass burning was a major factor leading to lower MACEC in other seasons. The average MACWS₋BᵣC at 365 nm was 1.4 ± 0.3 m² g⁻¹ with minimal seasonal variations. In contrast to MACEC, biomass burning was the main reason for a higher MACWS₋BᵣC in the non-monsoon season. The relative light absorption contribution of WS-BrC to EC was 9.9% over the 300–700 nm wavelength range, with a slightly higher ratio (13.6%) in the pre-monsoon season. Therefore, both EC and WS-BrC should be considered in the study of optical properties and radiative forcing of carbonaceous aerosols in this region.

The oxidation of magnetite into maghemite and its coating by natural organic constituents are common changes that affect the reactivity of iron oxide nanoparticles (IONP) in aqueous environments. Certain ubiquitous compounds such as humic acids (HA) and phosphatidylcholine (PC), displaying a high affinity for both copper (Cu) and IONP, could play a critical role in the interactions involved between both compounds. The adsorption of Cu onto four different IONP was studied: magnetite nanoparticles (magnNP), maghemite NP (maghNP), HA- and PC-coated magnetite NP (HA-magnNP and PC-magnNP, respectively). According to the results, the percentage of adsorbed Cu increases with increasing pH, irrespective of the IONP. Thus, protonation/deprotonation reactions are likely involved within Cu adsorption mechanism. Contrary to the other studied IONP, HA-magnNP favor Cu adsorption at most of the pH tested including acidic pH (pH = 3), suggesting that part of the active surface sites for Cu²⁺ were not grabbed by protons. The Freundlich adsorption isotherm of HA-magnNP provides the highest sorption constant KF (bonding energy) and n value which supports a heterogeneous sorption process. The heterogeneous adsorption between HA-magnNP and Cu²⁺ can be explained by both the diversity of the binding sites HA procured and the formation of multidendate complexes between Cu²⁺ and some of the HA functional groups. Such favorable adsorption process was neither observed on PC-coated-magnNP nor on maghNP, whose behaviors were comparable to that of magnNP. On another hand, HA and PC coatings considerably reduced iron (Fe) dissolution from magnNP as compared with magnNP. It was suggested that HA and PC coatings either provided efficient shield against Fe leaching or fostered dissolved Fe re-adsorption onto the functional groups at the coated magnNP surfaces. Thus, this study can help to better understand the complex interfacial reactions between cations-organic matter-colloidal surfaces which are relevant in environmental and agricultural contexts.This work showed that magnetite NP properties can be affected by surface modifications, which drive NP chemical stability and Cu adsorption, thereby affecting the global water chemistry.

Urine, which is an important waste biomass resource, is the main source of nitrogen in sewage and contains large quantities of emerging contaminants (ECs). In this study, we propose a new method to efficiently remove urine, simultaneously eliminate ECs, and control the generation of toxic chlorate during urine treatment using a photoelectrocatalytic-chlorine (PEC-Cl) system. A type-II heterojunction of WO₃/BiVO₄ was used as a photoanode to generate chlorine radicals (Cl•) by decreasing the oxidation potential of WO₃ valence band for the highly selective conversion of urine to N₂ and the simultaneous degradation of ECs in an efficient manner. The method presented surprising results. It was observed that the amount of toxic chlorate was significantly inhibited by circumventing the over-oxidation of Cl⁻ by holes or hydroxyl radicals (•OH). Moreover, the removal of urea nitrogen reached 97% within 90 min, while the degradation rate of trimethoprim in urine was above 98.6% within 60 min, which was eight times more than that in the PEC system (12.1%). Compared to the bare WO₃ photoanode, the toxic chlorate and nitrate generated by the WO₃/BiVO₄ heterojunction photoanode decreased by 61% and 44%, respectively. Thus, this study provides a safe, efficient, and environmentally-friendly approach for the disposal of urine.

Tea plants (Camellia sinensis (L.) O. Kuntze) can hyperaccumulate fluoride (F). The accumulation of F in tea leaves may induce serious health problems in tea consumers. It has been reported that selenium (Se) could reduce the accumulation of heavy metals in plants. Thus, the aim of this study was to investigate whether exogenous Se could reduce F accumulation in tea plant. The results showed that Se treatment could decrease F content in tea leaves, increase F accumulation in roots, decrease the proportion of water-soluble F in tea leaves and increase the Se content. Low F levels promoted the accumulation of Se in tea plants. Se treatment could modulate F-induced oxidative injury by decreasing malondialdehyde level and increasing the activities of superoxide dismutase, peroxidase and catalase. Moreover, Se inhibited F-induced increase in leaf iron, calcium, aluminum, leaf and root magnesium and lead contents. These results showed that Se application could decrease F content and increase Se content in tea leaves, which may be served as a novel strategy for production of healthy tea.

Artificial light at night (ALAN) changes the natural rhythm of light and darkness and can impair the biorhythms of animals, for example the nocturnal melatonin production of vertebrates, which serves as a proxy for daily physiological rhythms. Freshwater fish are exposed to ALAN in large urban and suburban areas in the form of direct light or in the form of skyglow, a diffuse brightening of the night sky through the scattered light reflected by clouds, atmospheric molecules, and particles in the air. However, investigations on the sensitivity of melatonin production of fish towards low intensities of ALAN in the range of typical skyglow are rare. Therefore, we exposed Eurasian perch (Perca fluviatilis) to nocturnal illumination levels of 0.01 lx, 0.1 lx and 1 lx and a control group with dark nights and daylight intensities of 2900 lx in all groups. After ten days of exposure to the experimental conditions, tank water was non-invasively sampled every 3 h over a 24 h period and melatonin was measured by ELISA. Melatonin was gradually reduced in all treatments with increasing intensity of ALAN whereas rhythmicity was maintained in all treatment groups although at 1 lx not all evaluated parameters confirmed rhythmicity. These results show a high sensitivity of Eurasian perch towards ALAN indicating that low light intensities of 0.01 lx and 0.1 lx as they occur in urban and suburban areas in the form of skyglow can affect the physiology of Eurasian perch. Furthermore, we highlight how this may impact perch in their sensitivity towards lunar rhythms and the role of skyglow for biorhythms of temperate freshwater fish.

Several epidemiological studies have evaluated the fractional exhaled nitric oxide (FeNO) of ambient air pollution but the results were controversial. We therefore conducted a systematic review and meta-analysis to investigate the associations between short-term exposure to air pollutants and FeNO level. We searched PubMed and Web of Science and included a total of 27 articles which focused on associations between ambient air pollutants (PM₁₀, PM₂.₅, black carbon (BC), nitrogen dioxide (NO₂), sulfur dioxide (SO₂), ozone (O₃)) exposure and the change of FeNO. Random effect model was used to calculate the percent change of FeNO in association with a 10 or 1 μg/m³ increase in air pollutants exposure concentrations. A 10 μg/m³ increase in short-term PM₁₀, PM₂.₅, NO₂, and SO₂ exposure was associated with a 3.20% (95% confidence interval (95%CI): 1.11%, 5.29%), 2.25% (95%CI: 1.51%, 2.99%),4.90% (95%CI: 1.98%, 7.81%), and 8.28% (95%CI: 3.61%, 12.59%) change in FeNO, respectively. A 1 μg/m³ increase in short-term exposure to BC was associated with 3.42% (95%CI: 1.34%, 5.50%) change in FeNO. The association between short-term exposure to O₃ and FeNO level was insignificant (P＞0.05). Future studies are warranted to investigate the effect of multiple pollutants, different sources and composition of air pollutants on airway inflammation.

Adding exogenous low-molecular weight organic acids is an effective technique to improve phytoremediation of Cd-contaminated soil and has been well documented, but how acid application rate affects remediation efficiency and its underlying limiting factors remains elusive. We investigated this using pot experiments with rapeseed (Brassica napus L.) as the model plant. Plastic pots packed with a sandy loam contaminated by Cd at 4.838 mg/kg were amended with acetic acid, oxalic acid, citric acid, malic acid and tartaric acid, respectively, at an application rate gradient varying from 0.0 to 12.0 mmol/kg. Plants in each pot were harvested after growing for five months, and we then measured the exchangeable, carbonate, Fe–Mn oxide, organic and residual Cd in the rhizosphere, as well as Cd in both roots and shoots. The results showed that all organic acids improved plant uptake of Cd and, compared with the control without acid addition, they could improve Cd uptake by more than 100%. The enhanced Cd extraction was due to the increase in exchangeable Cd in the rhizosphere. Plant Cd was weakly correlated to the amount of Cd lost from a unit volume of the rhizosphere due to root extraction (R² = 0.06), but a good negative correlation was found between them after normalizing the lost Cd by root biomass (R² = 0.36). Mass balance analysis revealed that the average Cd content in soil (rhizosphere and bulk soils combined) was much higher than the Cd content in the rhizosphere, and the improved Cd mobility after acid addition was thus due to the increased chelation. As diffusion of ligands in water is one order in magnitude smaller than diffusion of Cd ions, our results suggested that Cd migration from the bulk soil into the rhizosphere was a major factor limiting Cd phytoextraction by rapeseed after adding the exogenous organic acids.

Pharmaceuticals such as non-steroidal anti-inflammatory drugs (NSAIDs) have been found in the marine environment. Although there is a large body of evidence that pharmaceutical drugs exert negative impacts on aquatic organisms, especially in the freshwater compartment, only limited studies are available on bioconcentration and the effects of NSAIDs on marine organisms. Bivalves have a high ecological and socio-economic value and are considered good bioindicator species in ecotoxicology and risk assessment programs. Therefore, this review summarizes current knowledge on the bioconcentration and the effects of three widely used NSAIDs, diclofenac, ibuprofen and paracetamol, in marine bivalves exposed under laboratory conditions. These pharmaceutical drugs were chosen based on their environmental occurrence both in frequency and concentration that may warrant their inclusion in the European Union Watch List. It has been highlighted that ambient concentrations may result in negative effects on wild bivalves after long-term exposures. Also, higher trophic level organisms may be more impacted due to food-chain transfer (e.g., humans are shellfish consumers). Overall, the three selected NSAIDs were reported to bioconcentrate in marine bivalves, with recognized effects at different life-stages. Immune responses were the main target of a long-term exposure to the drugs. The studies selected support the inclusion of diclofenac on the European Union Watch List and highlight the importance of extending research for ibuprofen and paracetamol due to their demonstrated negative effects on marine bivalves exposed to environmental realistic concentrations, under laboratory conditions.

Improper land-use changes may lead to a loss of soil resources and cause environmental pollution. Chinese Torreya plantation (hereafter CTP) is an important cash tree plantation for nuts production in the mountainous areas of subtropical China. The increasing development of CTPs, to increase seed production, can result in the complete erasure of local natural vegetation.In this study, the vulnerability to soil erosion, loss of soil organic carbon (SOC) and nutrients in CTPs due to land-use change were evaluated. The results indicated that the rates of diffusive soil erosion in the young CTPs with extreme precipitation were about six-fold higher than with the natural vegetation. At sites with a similar slope, there was no significant difference in soil erosion levels between the young and old CTPs. The old CTPs did not hold significantly higher levels of SOC and soil total nitrogen (STN) in their topsoil when compared with the young CTPs. The natural mixed broadleaved subtropical forests lost about 35% of their SOC and 25% of their STN after they were converted into CTPs, but the CTPs had higher soil total phosphorus. The C: N ratios at the different sites were close to 11:1, but the N: P ratios were diverse. There were high levels of organic carbon, nitrogen and phosphorus in stream water. Adequate coverage of natural vegetation within or around the CTPs should be maintained to decrease soil erosion and nutrient loss. Suggestions to develop CTPs while protecting the environment are discussed. Overall, it was determined that aspects of the current management practices and strategies for developing CTPs should be changed to decrease soil erosion and nutrient loss.

China is one of the largest coastal countries in the world, which have all kinds of marginal systems. Studies have reported the sedimentary Polycyclic aromatic hydrocarbons (PAHs) pollution status, including their concentrations, sources and risks, in localized marginal systems, which showed significant differences. Thus, a comprehensive understanding of their pollution in marginal systems along China Mainland is urgently needed on a national scale. In the present study, the concentrations of 16 priority PAHs in surface sediments from 62 different marginal systems along China Mainland were reviewed. Their sources were identified and apportioned, and the health risks and ecological risks were also evaluated. As a result, the total sedimentary PAHs varied in a wide range of 4–3700 ng/g, with the lowest values observed in Kenting National Park in East China Sea and the highest values observed in Daliao River estuary in Bohai Sea. Their concentrations suggested that they were not contaminated-weakly contaminated in most study areas, but were contaminated-heavily contaminated in some pollution hot-spots. Source identification and apportion suggested that the sedimentary PAHs were mainly originated from coal combustion, vehicular emission, natural gas combustion and petrogenic source, but the coal combustion and vehicular emission contributed most to their emission (>90%). Risk assessment suggested that the carcinogenic risks were lower than the upper limit of the acceptable range (10⁻⁴), which were acceptable at a large spatial scale. However, for sediments from Qinhuangdao coastal wetland, Daliao River estuary and Yangpu Bay, their carcinogenic risks were higher than 10⁻⁴, which will pose high carcinogenic risks for adults. The non-carcinogenic risks were acceptable in all marginal systems with values lower than the safety guideline (<1). In the ecological risk assessment, their concentrations in some pollution hot-spots were higher than the safety guidelines (effects range low, ERL), suggesting a higher potential ecological risk.