Rare earth elements (REEs) are widely used in optoelectronic industries, and they can be emitted into the environment and may induce biological effects. In this study, we investigated the provenance and bioaccessibility of REEs in atmospheric particles (APs) collected from areas impacted by the optoelectronic industry. The geoaccumulation index (Igₑₒ) values showed that Y, Eu, and Tb were much more enriched in the APs from the optoelectronic recycling sites than in those from the optoelectronic producing sites and were not enriched in the APs from the optoelectronic administrative sites and background sites. The characteristic parameters and the distribution patterns of REEs demonstrated that the AP samples from the recycling sites and producing sites showed remarkably positive Eu and Tb anomalies. According to the positive matrix factorization (PMF) model, the optoelectronic industry was quantitatively determined to contribute 82.8% of Y, 86.5% of Eu, and 83.4% of Tb. Furthermore, an in vitro physiologically based extraction test (PBET) was performed to assess the bioaccessibility of REEs in the APs. The results showed that the bioaccessibility of all the REEs in the APs was below 50.0% in the human gastrointestinal tract, with higher values in the gastric phases than in the intestinal phases. In particular, extremely low gastric bioaccessibilities of Tb and Ce and relatively high gastric bioaccessibilities of Y and Eu were observed in the APs from the recycling sites and producing sites, which may due to the chemical composition of the compounds containing REEs that are used in the optoelectronic industry. In conclusion, our results provide additional information about the contribution and influence of the optoelectronic industry on the provenance and bioaccessibility of REEs in APs.

This paper presents the results of the study on columnar aerosol optical and physical properties and radiative effects directly observed over Dushanbe, the capital city of Tajikistan, a NASA AERONET site (equipped with a CIMEL sunphotometer) in Central Asia. The average aerosol optical depth (AOD) and Ångström exponent (AE) during the observation period from July 2010 to April 2018 were found to be 0.28 ± 0.20 and 0.82 ± 0.40, respectively. The highest seasonal AOD (0.32 ± 0.24), accompanied by the lowest average AE (0.61 ± 0.25) and fine-mode fraction in AOD (0.39), was observed during summer due to the influence of coarse particles like dust from arid regions. Fine particles were found in significant amounts during winter. The ‘mixed aerosol’ was identified as the dominant aerosol type with presence of ‘dust aerosol’ during summer and autumn seasons. Aerosol properties like volume size distribution, single scattering albedo, asymmetry parameter and refractive index suggested the influence of coarse particles (during summer and autumn). Most of the air masses reaching this site transported local and regional emissions, including from beyond Central Asia, explaining the presence of various aerosol types in Dushanbe’s atmosphere. The seasonal aerosol radiative forcing efficiency (ARFE) in the atmosphere was found high (>100 Wm⁻²) and consistent throughout the year. Consequently, this resulted in similar seasonally coherent high atmospheric solar heating rate (HR) of 1.5 K day⁻¹ during summer-autumn-winter, and ca. 0.9 K day⁻¹ during spring season. High ARFE and HR values indicate that atmospheric aerosols could exert significant implications to regional air quality, climate and cryosphere over the central Asian region and downwind Tianshan and Himalaya-Tibetan Plateau mountain regions with sensitive ecosystems.

Although human exposure to polycyclic aromatic hydrocarbons (PAH) has been associated with in vivo oxidative damage, and hydroxyPAH metabolites have been used as biomarkers to assess PAH-induced oxidative stress, few studies have looked at the likely causative compounds for oxidative stress in humans - PAH quinones. We developed a method using pre-column derivatization - liquid chromatography-heated electrospray ionization-tandem mass spectrometry (LC-HESI-MS/MS) to analyze ortho-phenanthrene quinones (PheQs) in human urine. 1,2-PheQ and 3,4-PheQ were identified and quantified in 3 mL of human urine; their total concentrations were higher in cigarette smokers (0.79 ± 0.98 nmol/6h urine) than in nonsmokers (0.20 ± 0.98 nmol/6h urine) (p < 0.01). The total of 1,2-PheQ and 3,4-PheQ were more strongly correlated with urinary (Z)-7-[1R,2R,3R,5S)-3,5-dihydroxy-2-[(E,3S)-3-hydroxyoct-1-enyl]cyclopentyl]hept-5-enoic acid (8-iso-PGF₂α), a biomarker of lipid peroxidation (R² = 0.53, p < 0.001), than the other phenanthrene metabolites including phenanthrene tetraol (PheT), phenanthrene-1,2-dihydrodiol (1,2-PheD), and total phenanthrene phenols (OHPhe), consistent with the concept that PheQs and likely other PAH quinones play a causal role in the generation of reactive oxygen species (ROS) in humans. Thus, PheQs may be suitable as biomarkers to assess human exposure to oxygenated PAH and the subsequent oxidative damage. This study provides unique support, by analysis of human urinary metabolites, for the PAH quinone mediated oxidative damage hypothesis of PAH carcinogenesis.

Contamination of the Technology Critical Elements (TCE) through e-wastes and beach plastic wastes are some of the attributes to the recent rise in marine pollution. A generalized study of pollutants in the marine waters showed no evidence of the effect of TCE. However, an in-depth study revealed the mean TCE concentrations in the sequence of gallium (Ga) > thallium (Tl) > niobium (Nb) > tellurium (Te) > tantalum (Ta) > germanium (Ge) > indium (In) in wastewater (0.38 ng.L⁻¹) >sediment (0.3 ng g⁻¹) e-wastes (0.29 ng g⁻¹) > coastal water (0.26 ng.L⁻¹) > plastic wastes (0.133 ng g⁻¹) >fish (0.13 ng g⁻¹). The mean site-wise analysis of all the samples showed high TCE during winter than in the summer seasons as well, in the sequence of Site-II>Site-I>Site-V>Site-IV>Site-III. The mean distribution coefficient (Kd) of TCE was high in the summer (1.95) than during the winter (1.60) seasons but, the reverse seasonal effects were observed with the bioavailability (%BA) and geo-accumulation index (Igₑₒ). This index quantified TCE in e-wastes and plastic materials. Furthermore, these indicators labeled TCE as one among the sources for ‘Fish Kill,’ a futuristic threat to seafood consumers and a biomonitoring tool to marine pollution.

Soils, especially permafrost in the Arctic and the Tibetan Plateau, are one of the largest reservoirs of mercury (Hg) in the global environment. The Hg concentration in the grassland soils over the Tibetan Plateau and its driving factors have been less studied. This study analyzes soil total mercury (STHg) concentrations and its vertical distribution in grassland soil samples collected from the Tibetan Plateau. We adopt a nested-grid high-resolution GEOS-Chem model to simulate atmospheric Hg deposition. The relationship between STHg and soil organic carbon (SOC), as well as atmospheric deposition, are explored. Our results show that the STHg concentrations in the Tibetan Plateau are 19.8 ± 12.2 ng/g. The concentrations are higher in the south and lower in the north in the Tibetan Plateau, consistent with the previous results. Our model shows that the average deposition flux of Hg is 3.3 μg m⁻² yr⁻¹, with 57% contributed by dry deposition of elemental mercury (Hg⁰), followed by dry (19%) and wet (24%) deposition of divalent mercury. We calculate the Hg to carbon ratio (RHg:C) as 5.6 ± 6.5 μg Hg/g C, and the estimated STHg is 86.6 ± 101.2 Gg in alpine grasslands in the Tibetan Plateau. We find a positive relationship between STHg and SOC in the Tibetan Plateau (r² = 0.36) and a similar positive relationship between STHg and atmospheric total Hg deposition (r² = 0.24). A multiple linear regression involving both variables better model the observed STHg (r² = 0.42). We conclude that SOC and atmospheric deposition influence STHg simultaneously in this region. The data provides information to quantify the size of the soil Hg pool in the Tibetan Plateau further, which has important implications for the Hg cycles in the permafrost regions as well as on the global scale.

The potential influence of microplastic debris on marine organisms is an issue of great ecological and socioeconomic concern. Experiments exposing fishes and invertebrates to constant concentrations of microplastics often yield high variation in particle ingestion rates among individuals. Yet, despite an increasing interest in microplastic ingestion in the wild, the potential intrinsic drivers of inter-individual variation have received little attention so far. Here we assessed individual-level ingestion of Polyethylene microspheres by laboratory-reared juvenile anemonefish, Amphiprion ocellaris, in relation to (a) ambient particle concentrations and (b) repeatable behavioural traits. We show that microplastic ingestion is highly variable at all tested particle concentrations and that this variation can partially be explained by individual activity levels. Moreover, the relationship between ingestion and behavioural variation increased notably when only the most behaviourally consistent individuals (n = 40 out of 60) were considered in the analysis. Our findings indicate that microplastic ingestion rates in juvenile reef fishes may be less dependent on ambient concentrations than expected; instead they are to some degree phenotype-dependent. Care should thus be taken when reporting mean responses to microplastic exposure treatments, because some individuals may not be affected in the same way as others due to differential ingestion behaviour. We also discuss potential ramifications of non-random ingestion variability on population- and community-level responses.

The Keban Dam Reservoir, located on the Euphrates River, is the second largest reservoir of Turkey. Water quality of this reservoir is of great importance because it is widely used for recreation, aquaculture production, fishing, and irrigation. In this study, discriminant analysis, principal component analysis (PCA), factor analysis (FA) and cluster analysis (CA) were conducted to evaluate the seasonal and spatial variations in surface water quality of the reservoir. Also, total phosphorus (TP) content in sediments, water type and trophic status of the reservoir were determined. For this, 19 water quality variables and TP in sediments were monitored seasonally at 11 sampling stations on the reservoir during one year. Hierarchical CA classified 11 stations into three groups, i.e., upstream (moderate polluted), midstream (low polluted) and downstream (clean) regions. PCA/FA allowed to group the variables responsible for variations in water quality, which are mainly related to mineral dissolution (natural), organic matter and nutrients (anthropogenic), and physical parameters (natural). Discriminant analysis (DA) gave better results for both data reduction and spatio-temporal analysis. Stepwise temporal DA identified eight variables: water temperature (WT), chemical oxygen demand (COD), nitrate nitrogen (NO₃–N), soluble reactive phosphorus (SRP), chlorophyll-a (Chl-a), potassium (K⁺), magnesium (Mg²⁺), and calcium (Ca²⁺), which are the most significant variables responsible for temporal variations in water quality of the reservoir, while stepwise spatial DA identified three variables: K⁺, chloride (Cl⁻), and sulphate (SO₄⁻²), which are the most significant variables responsible for spatial variations. According to Ontario sediment-quality guidelines, sediments of the reservoir can be considered as unpolluted in terms of mean TP content. The water type of the reservoir was calcium-bicarbonate. According to trophic state index values based on TP and Chl-a, upstream region (moderate polluted) of the reservoir was in the eutrophic status, whereas other regions were in the mesotrophic status.

As a well-known toxic element, antimony occurred in a wide range of concentrations in the geothermal waters discharging from Rehai and Daggyai, two representative hydrothermal areas in the Yunnan-Sichuan-Tibet Geothermal Province of China. Antimony speciation in different types of the hot springs in Rehai and Daggyai varied greatly as well, and tri- and tetrathioantimonate were detected in most neutral to alkaline Rehai hot springs. Neutral to alkaline pH, high sulfide concentrations, and high sulfide to antimony ratios were the critical factors promoting the formation of thioantimonates. The fact that no thioantimonates were detected in neutral to alkaline Daggyai hot springs is attributed to high concentrations of coexistent arsenic capable of inhibiting the thiolation of oxyantimony anions, because thioantimonates are kinetically more labile than thioarsenates. Upon discharge of the hot springs, both total aqueous antimony and arsenic decreased rapidly and substantially via immobilization to the sediments in the spring vents and their outflow channels. Some of the common iron-bearing minerals in the spring sediments, like pyrite and goethite, are known sinks for antimony and arsenic. Yet, an interesting difference was observed with antimony and iron contents in the sediment samples showing a significant correlation that was lacking for arsenic and iron contents. The explanation might be that for arsenic, sorption affinities are known to vary significantly with aqueous arsenic speciation and mineral phases. Typically, thiolation increases, and oxidation decreases arsenic mobility. Sorption experiments for antimony conducted in the present study, in contrast, showed that different antimony species were comparably sorbed to pyrite over a wide range of initial antimony concentrations and to goethite at relatively low initial antimony concentrations (but still covering the concentration range of antimony in common natural waters), so neither thiolation nor oxidation contributed significantly to the mobility of antimony in the hot springs investigated in this study.

Emissions from the crop residue burning adversely affect the regional and global air quality including public health. In this study, a district-wise comprehensive emission inventory of key pollutants (PM₂.₅, PM₁₀, CO, CO₂, SO₂, NOx, N₂O, NH₃, CH₄, NMVOC, EC, OC, PAH) emitted during primary crop residue burning was developed using activity data for the major agrarian states of north India for the agricultural year 2017–18. The emissions were scaled to the spatial resolution of 1 km grid to study the spatial distribution of crop residue burning activities using VIIRS Thermal anomalies datasets. An estimated 20.3 Mt and 9.6 Mt of crop residue were burned in Punjab and Haryana, resulting in an emission of 137.2 Gg and 56.9 Gg of PM₂.₅ and 163.7 Gg and 72.1 of PM₁₀ Gg for respective states. The emissions of EC, OC, and PAHs were 8.6 Gg, 45.7 Gg, and 0.08 Gg in Punjab, whereas in Haryana emissions were 3.7 Gg, 17.7 Gg, and 0.03 Gg, respectively. The results show that rice and wheat crops were major contributor to residue burnt at the field (>90%) leading to the high load of atmospheric emissions in the IGP region. Further, CO₂ equivalent greenhouse gas emissions were 34.8 Tg and 17.3 Tg for Punjab and Haryana, respectively. Around 30000 and 8500 active fires were detected by VIIRS over the agricultural area of Punjab and Haryana during the studied year. The GIS-based bottom-up approach using gridded emission inventory shows pollutant distribution dominates over the south-western part of Punjab and north-western region of Haryana. The proximity of these regions to Delhi and transboundary movement of emissions towards Indo-Gangetic plains causes high air pollution episodes. The high-resolution inventory of various pollutants will be useful for regional air quality models to better predict and manage the hotspot of air pollution.

Wildfires may play a role in redistributing radionuclides in the environment in combination with hydrological processes such as surface runoff and soil erosion. We investigated plot-scale radionuclide wash-off at forest sites affected by wildfires in the Chernobyl Exclusion Zone (CEZ). We also compared speciation of the washed-off radionuclides with those in previous studies conducted just after the accident in 1986. We observed the surface runoff and the radionuclide wash-off with a soil erosion plot at forest and post-fire sites during May–September 2018. In the post-fire site, 2.81 mm of surface runoff was observed in at least three flow events resulting from 285.8 mm total rainfall. The fluxes of dissolved and particulate ¹³⁷Cs were estimated as 4.9 and 161 Bq m⁻², respectively. The dissolved phase ⁹⁰Sr flux was estimated as 214 Bq m⁻². At the forest site, a single surface runoff (0.67 mm) event was generated by rainfall of 182.2 mm. The fluxes of dissolved and particulate ¹³⁷Cs wash-off values were 6.2 and 8.6 Bq m⁻², respectively. The flux of dissolved ⁹⁰Sr wash-off from the forest was estimated as 45.1 Bq m⁻². The distribution coefficient, which indicates the dissolved-particulate form of radionuclides, in the post-fire site was 30 times higher than that in the forest site, indicating the importance of particulate ¹³⁷Cs wash-off after fire in the CEZ. The entrainment coefficients for dissolved and particulate ¹³⁷Cs concentrations were around 50 times lower than those obtained in the corresponding position within the CEZ immediately after the accident in 1987. The effect of downward migration of ¹³⁷Cs over 30 years led to decreased entrainment coefficients for dissolved and particulate ¹³⁷Cs. The effect of downward migration of radionuclides was considered sufficient to indicate changes in normalized liquid and solid radionuclides wash-off entrainment coefficient and the distribution coefficient in this study.