While determining the uranium concentration in the rock (background level) and soils on the Iberian Massif of western Spain, several geochemical anomalies were observed. The uranium concentration was much higher than the geochemical levels at these locations, and several uranium minerals were detected. The proposed uranium background levels for natural soils in the west of Salamanca Province (Spain) are 29.8 mg kg−1 in granitic rock and 71.2 mg kg−1 in slate. However, the soil near the tailings of abandoned mines exhibited much higher concentrations, between 207.2 and 542.4 mg kg−1.The calculation of different pollution indexes (Pollution Factor and Geo-accumulation Index), which reveal the conditions in the superficial horizons of the natural soils, indicated that a good percentage of the studied samples (16.7–56.5%) are moderately contaminated. The spatial distribution of the uranium content in natural soils was analysed by applying the inverse distance weighted method.The distribution of uranium through the horizons of the soils shows a tendency to accumulate in the horizons with the highest clay content. The leaching of uranium from the upper horizons and accumulation in the lower horizons of the soil could be considered a process for natural attenuation of the surface impacts of this radiogenic element in the environment. Environmental restoration is proposed in the areas close to the abandoned mining facilities of this region, given the high concentration of uranium. First, all the tailings and other mining waste would be covered with a layer of impermeable material to prevent leaching by runoff. Then, a layer of topsoil with organic amendments would be added, followed by revegetation with herbaceous plants to prevent surface erosion.

Antibiotics residuals in the environments receive wide concerns due to the high risk of generating antibiotic resistance. Natural organic matters (NOM) existed in the environments are considered to have the capacity of binding with organic contaminants, consequently influencing their speciation and transformation in the natural environments. To assess the migration of antibiotics in the environments, it is crucial to understand the binding mechanisms between NOM and antibiotics, which is still unclear due to the limit of available research methods. In this study, the interaction between fulvic acids (FA), one of the main components of NOM, and sulfamethazine (SMZ) was characterized by nuclear magnetic resonance (NMR) combined with surface plasmon resonance (SPR) and isothermal titration calorimetry (ITC) technology. The parameters related to kinetics and thermodynamics of the interaction were determined, and the possible mechanisms driving the interaction were also proposed. In addition, density functional theory (DFT) was used to predict the binding mode between FA and SMZ to reveal the interaction mechanism. Results indicate that FA can effectively bound with SMZ to form a stable complex with a binding constant at the level of 10³ L/mol. The kinetic parameters including association and dissociation constants were 29.4 L/mol/s and 6.64 × 10⁻³ 1/s, respectively. Hydrophobic interaction might play significant roles in the binding interaction with ancillary contribution of π-π conjunction arising from the aromatic rings stacking of FA and SMZ.

There is considerable interest in applying omics techniques, which have proven extremely valuable for laboratory-based toxicology studies, towards field-scale ecotoxicology and environmental monitoring. Concerns that confounding factors in natural ecosystems may exacerbate variability in omics datasets must be addressed to validate the transition from laboratory to field. This study explores how temporal variability related to seasonal and climatic trends influence qualitative and quantitative metabolomics outcomes, in fish from reference and metal(loid)-polluted wetlands in Australia. Female mosquitofish (Gambusia holbrooki) were sampled on two separate occasions, from a rehabilitated tailings wetland at the site of historic antimony (Sb) processing and a reference wetland with comparable water quality. The first sampling coincided with greater monthly rainfall and colder water temperature, whereas the second sampling was drier and water was warmer. Despite temporal changes and associated differences in metal(loid) concentrations, site differences in metabolite profiles were qualitatively very similar between sampling events. However, quantitative differences were observed, with a greater number of significantly altered metabolites identified during the second sampling event, which coincided with greater metal(loid) concentrations in both water and fish. The majority of identified metabolites were elevated in fish from the contaminated wetland, but with notable decreases in several metabolites that are known to play a role in various aspects of metal(loid) binding, detoxification and excretion. Specifically, decreased aspartate, histidine, myo-inositol, taurine and choline were observed in fish from the contaminated wetland, and may therefore represent a metabolite suite that is broadly indicative of metal toxicity. Quantitative differences between sampling events are suggestive of a dose-response relationship observable at the cellular level which, if harnessed, may be useful for assigning levels of concern based on the degree of change in a multi-parameter set of metabolite biomarkers.

The oxidative potential (OP) and chemical characteristics of fine particles collected from urban, roadside, rural, and industrial sites in Korea during spring, summer, fall, and winter seasons and an urban site in the Philippines during dry and wet seasons were examined. Significant differences in the OP of fine particles among sites and seasons were found. The industrial site yielded the highest OP activity (both mass and volume-normalized OP) among the sites, suggesting the strongest reactive oxygen species (ROS)-generating capability of industry source-dominant PM₂.₅. Seasonal data show that OP activities increased during the spring and summer possibly due to increased heavy metals caused by dust events and secondary organic aerosols formed by strong photochemical activity, respectively. The strength of the OP association with the chemical components highlights the influence of organic carbon and transition metals on the OP of ambient fine particles. The two OP assays (dithiothreitol (DTT) and electron spin resonance (ESR)) having different ROS-generating mechanisms were found to have different sensitivities to the chemical components facilitating a complementary analysis of the OP of ambient fine particles. Multiple linear regression model equations (OP as a function of chemical components) which were dependent on the sites were derived. A comparison of the daily OP and hazard index (HI) (the ratio of the measured mass concentration to the reference mass concentration of fine particles) suggests that the HI may not be sufficient to accurately estimate the health effects of fine particles, and a direct or indirect measurement of toxicity such as OP should be required in addition to the concentration level.

Selenium in the lower Athabasca River (Alberta, Canada) is of concern due to potential inputs from the weathering of shallow bitumen deposits and emissions from nearby surface mines and upgraders. Understanding the source of this Se, however, is complicated by contributions from naturally saline groundwater and organic matter-rich tributaries. As part of a two-year multi-disciplinary study to assess natural and anthropogenic inputs, Se and its chemical speciation were determined in water samples collected along a ∼125 km transect of the Athabasca River and associated tributaries. Selenium was also determined in the muscle of Trout-perch (Percopsis omiscomaycus), a non-migratory fish species, that were sampled from selected locations. Dissolved (<0.45 μm) Se in the Athabasca River was consistently low in 2014 (0.11 ± 0.02 μg L⁻¹; n = 14) and 2015 (0.16 ± 0.02 μg L⁻¹; n = 21), with no observable increase from upstream to downstream. Selenate was the predominant inorganic form (∼60 ng L⁻¹) and selenite was below detection limits at most locations. The average concentration of Se in Trout-perch muscle was 2.2 ± 0.4 mg kg⁻¹ (n = 34), and no significant difference (p > 0.05) was observed between upstream and midstream (industrial) or downstream reaches. Tributary waters contained very low concentrations of Se (typically < 0.1 μg L⁻¹), which was most likely present in the form of dissolved organic colloids.

The change in land-use from woodland to crop production leads to increased nitrous oxide (N2O) emissions. An understanding of the main N2O sources in soils under a particular land can be a useful tool in developing mitigation strategies. To better understand the effect of land-use on N2O emissions, soils were collected from 5 different land-uses in southeast China: shrub land (SB), eucalyptus plantation (ET), sweet potato farmland (SP), citrus orchard (CO) and vegetable growing farmland (VE). A stable isotope experiment was conducted incubating soils from the different land use types at 60% water holding capacity (WHC), using 15NH4NO3 and NH415NO3 to determine the dominant N2O production pathway for the different land-uses. The average N2O emission rates for VE, CO and SP were 5.30, 4.23 and 3.36 μg N kg−1 dry soil d−1, greater than for SB and ET at 0.98 and 1.10 μg N kg−1 dry soil d−1, respectively. N2O production was dominated by heterotrophic nitrification for SB and ET, accounting for 51 and 50% of N2O emissions, respectively. However, heterotrophic nitrification was negligible (<8%) in SP, CO and VE, where autotrophic nitrification was a primary driver of N2O production, accounting for 44, 45 and 66% for SP, CO and VE, respectively. Denitrification was also an important pathway of N2O production across all land-uses, accounting for 35, 35, 49, 52 and 32% for SB, ET, SP, CO and VE respectively. Average N2O emission rates via autotrophic nitrification, denitrification and heterotrophic nitrification increased significantly with gross nitrification rates, NO3− contents and C:N ratios respectively, indicating that these were important factors in the N2O production pathways for these soils. These results contribute to our understanding and ability to predict N2O emissions from different land-uses in subtropical acidic soils and in developing potential mitigation strategies.

We used replicated paddy microcosm systems to estimate the tropic transfer of citrate-coated silver nanoparticles (AgNP citrate), polyvinylpyrrolidone (PVP)-coated AgNP (AgNP PVP), and silver ions (AgNO₃) for 14 days under two exposure regimes (a single high-dose exposure; 60 μg L⁻¹ and a sequential low-dose exposure at 1 h, 4 days and 9 days; 20 μg L⁻¹ × 3 = 60 μg L⁻¹). Most Ag ions from AgNO₃ had dispersed in the water and precipitated partly on the sediment, whereas the two Ag NPs rapidly coagulated and precipitated on the sediment. The bioconcentration factors (BCFs) of Ag from AgNPs and AgNO₃ in Chinese muddy loaches and biofilms were higher than those of river snails in both exposure conditions. These BCFs were more prominent for 14 days exposure (7.30 for Chinese muddy loach; 4.48 for biofilm) in the low-dose group than in the single high-dose group. Their retention of AgNPs and Ag ions differed between the two exposure conditions, and uptake and elimination kinetics of Ag significantly differed between AgNP citrate and AgNP PVP in the sequential low-dose exposure. Stable isotopes analyses indicated that the trophic levels between Chinese muddy loaches and biofilms and between river snails and biofilms were 2.37 and 2.27, respectively. The biomagnification factors (BMFs) of AgNPs and AgNO₃ between Chinese muddy loaches and biofilms were significantly higher than those between river snails and biofilms under both exposure settings. The BMFs of AgNP citrate and AgNO₃ between Chinese muddy loaches and biofilms were greater than those of AgNP PVP for 14 days in the single high-dose group, whereas the BMFs of AgNP PVP were greater than those of AgNP citrate and AgNO₃ in the sequential low-dose group. These microcosm data suggest that AgNPs have the potential to impact on ecological receptors and food chains.

Benzo(a)pyren-7,8-dihydrodiol-9,10-epoxide (BPDE) is an endocrine disrupter and ultimate carcinogenic product of benzo(a)pyrene (BaP). Numerous studies have shown that BPDE causes trophoblast-related diseases, such as preeclampsia, growth restriction or miscarriages. However, the underlying mechanism, especially the mitochondria-related BPDE-induced trophoblast dysfunction remains unknown. In this study, we examined mitochondrial functions in BPDE-induced human trophoblast cell line Swan 71. BPDE decreased cell ability, attenuated cell invasion and HCG secretion, induced cell apoptosis, decreased mitochondrial membrane potential, increased reactive oxygen species (ROS) and MDA, and decreased SOD activity in a dose-dependent manner. In the mechanism, BPDE significantly increased pro-apoptosis protein (P53 and Bak1) and decreased anti-apoptosis protein (Bcl-2). Furthermore, the protein expression levels of mitochondrial fusion genes (Mfn1, Mfn2, and OPA1) were decreased and those of fission genes (Fis1 and Drp1) were increased with increasing concentrations of BPDE and incubation time, resulting in the release of Cyt c and activation of Caspase 3, which irreversibly induced trophoblast cell apoptosis. This study reveals the mechanism of dysfunction of trophoblast cells through cell apoptosis due to the disorder of mitochondrial fission/fusion after exposure to BPDE, providing a further experimental understanding the adverse effects of BaP on trophoblast cells in early pregnancy.

A Community Multiscale Air Quality (CMAQ) model with source-oriented lumped SAPRC-11 (S11L) photochemical mechanism and secondary organic aerosol (SOA) module was applied to determine the contributions of anthropogenic and biogenic sources to SOA concentrations in China. A one-year simulation of 2013 using the Multi-resolution Emission Inventory for China (MEIC) shows that summer SOA are generally higher (10–15 μg m−3) due to large contributions of biogenic (country average 60%) and industrial sources (17%). In winter, SOA formation was mostly due to anthropogenic emissions from industries (40%) and residential sources (38%). Emissions from other countries in southeast China account for approximately 14% of the SOA in both summer and winter, and 46% in spring due to elevated open biomass burning in southeast Asia. The Regional Emission inventory in ASia v2.1 (REAS2) was applied in this study for January and August 2013. Two sets of simulations with the REAS2 inventory were conducted using two different methods to speciate total non-methane carbon into model species. One approach uses total non-methane hydrocarbon (NMHC) emissions and representative speciation profiles from the SPECIATE database. The other approach retains the REAS2 speciated species that can be directly mapped to S11L model species and uses source specific splitting factors to map other REAS2 lumped NMHC species. Biogenic emissions are still the most significant contributor in summer based on these two sets of simulations. However, contributions from the transportation sector to SOA in January are predicted to be much more important based on the two REAS2 emission inventories (∼30–40% vs. ∼5% by MEIC), and contributions from residential sources according to REAS2 was much lower (∼21–24% vs. ∼42%). These discrepancies in source contributions to SOA need to be further investigated as the country seeks for optimal emission control strategies to fight severe air pollution.

Nitrous oxide (N₂O) is a major greenhouse gas, with elevated emission being reported from subtropical forests that receive high nitrogen (N) deposition. After 10 years of monthly addition of ammonium nitrate (NH₄NO₃) or sodium nitrate (NaNO₃) to a Mason pine forest at Tieshanping, near Chongqing city in Southwest China, the simulated N deposition was stopped in October 2014. The results of soil N₂O emissions monitoring in different seasons during the nitrogen application period showed that nitrogen addition significantly increased soil N₂O emission. In general, the N₂O emission fluxes were positively correlated to nitrate (NO₃⁻) concentrations in soil solution, supporting the important role of denitrification in N₂O production, which was also modified by environmental factors such as soil temperature and moisture. After stopping the application of nitrogen, the soil N₂O emissions from the treatment plots were no longer significantly higher than those from the reference plots, implying that a decrease in nitrogen deposition in the future would cause a decrease in N₂O emission. Although the major forms of N deposition, NH₄⁺ and NO₃⁻, had not shown significantly different effects on soil N₂O emission, the reduction in NH₄⁺ deposition may decrease the NO₃⁻ concentrations in soil solution faster than the reduction in NO₃⁻ deposition, and thus be more effective in reducing N₂O emission from N-saturated forest soil in the future.