Nitrogen pollution of groundwater has created problems worldwide. Riparian zones form a connection hub for terrestrial and aquatic ecosystems. As a potential source of ammonium in groundwater, aquitards have an important effect on the environment of riparian zones. The spatial distribution and factors influencing the ammonium content in the riparian zone aquitard of a small watershed were analyzed through three geological boreholes with increasing distances from the river: boreholes A > B > C. The results show that the distribution of ammonium was closely related to the lithology of sediments. Under the influence of the river and floods, the average content of ion exchange form of ammonium of sediments in borehole A (stable sedimentary environment) was 94.31 mg kg⁻¹, accounting for 21.2% of the transferable ammonium. The average proportions of ion exchange form of ammonium in the transferable ammonium of boreholes B and C (unstable sedimentary environment) were 19.1% and 17.4%, respectively. The carbonate and iron-manganese oxide forms of ammonium content of sediments in three boreholes were 0.96–15.28 mg kg⁻¹ and 2.3–54.4 mg kg⁻¹, respectively; this was mainly affected by the pH and Eh of the sedimentary environment. Organic sulfide, the form of transferable ammonium of sediments mainly exists in organic matter. The ammonium content in pore water generally increased with depth and was mainly derived from the mineralization of humic-like organic matter in borehole A. The ammonium in pore water in boreholes B and C mixed with ammonium from the mineralization of organic matter and the desorption of ion exchange form ammonium within sediments. The ammonium content in the pore water (up to 5.34 mg L⁻¹) was much higher than the limit for drinking water of 0.5 mg L⁻¹ in China. Therefore, the aquitard has a high risk of releasing ammonium and poses a certain threat to the quality of groundwater.

Polybrominated diphenyl ethers (PBDEs) serve as flame retardants in many household materials such as electrical and electronic devices, furniture, textiles, plastics, and baby products. Though the use of PBDEs like penta-, octa- and deca-BDE greatly reduces the fire damage, indoor pollution by these toxic emissions is ever-growing. In fact, a boom in the global market projections of PBDEs threatens human health security. Therefore, efforts are made to minimize PBDEs pollution in USA and Europe by encouraging voluntary phasing out of the production or imposing compelled regulations through Stockholm Convention, but >500 kilotons of PBDEs still exist globally. Both ‘environmental persistence’ and ‘bioaccumulation tendencies’ are the hallmarks of PBDE toxicities; however, both these issues concerning household emissions of PBDEs have been least addressed theoretically or practically. Critical physiological functions, lipophilicity and toxicity, trophic transfer and tissue specificities are of utmost importance in the benefit/risk assessments of PBDEs. Since indoor debromination of deca-BDE often yields many products, a better understanding on their sorption propensity, environmental fate and human toxicities is critical in taking rigorous measures on the ever-growing global deca-BDE market. The data available in the literature on human toxicities of PBDEs have been validated following meta-analysis. In this direction, the intent of the present review was to provide a critical evaluation of the key aspects like compositional patterns/isomer ratios of PBDEs implicated in bioaccumulation, indoor PBDE emissions versus human exposure, secured technologies to deal with the toxic emissions, and human toxicity of PBDEs in relation to the number of bromine atoms. Finally, an emphasis has been made on the knowledge gaps and future research directions related to endurable flame retardants which could fit well into the benefit/risk strategy.

A major health scandal involving DEHP-tainted (di-2-ethylhexyl phthalate) foodstuffs occurred in Taiwan in 2011. We investigated temporal relationships between urinary DEHP metabolites and biomarkers of oxidative stress in two cohorts of potentially affected children during that food scandal. One cohort was collected from Kaohsiung Medical University Hospital in southern Taiwan between May and June of 2011 (the KMUH cohort). This cohort was followed up at 2, 6, and 44 months. The other cohort was collected from a nationwide health survey conducted by Taiwan’s National Health Research Institutes (the NHRI cohort) for potentially affected people between August 2012 and January 2013. Both cohorts only included children 10 years old and younger who had provided enough urine for analysis of urinary DEHP oxidative metabolites and two markers of oxidative stress: 8-oxo-2′-deoxyguanosine (8-OHdG) and malondialdehyde (MDA). The KMUH cohort had a simultaneous and significant decrease in urinary DEHP metabolites, 8-OHdG, and MDA, with the lowest concentrations found at the 6-month follow up and maintained until the 44-month follow up, consistent with those from NHRI cohort at ∼15–18 months post-scandal (p > 0.05). There were decreases in both DEHP metabolites and oxidative stress markers across the populations, but no association was observed between DEHP metabolites and oxidative stress markers in individuals in the two cohorts. Continued follow-up is needed to determine long-term health consequences in these children.

As glyphosate-based herbicides, sold under the commercial name Roundup®, represent the most used herbicides in the world, contamination of the freshwater environment by glyphosate has become a widespread issue. In Italy, glyphosate was detected in half of the surface waters monitoring sites and its concentrations were higher than environmental quality standards in 24.5% of them. It can last from days to months in water, leading to exposure for aquatic organisms and specifically to amphibians’ larvae that develop in shallow water bodies with proven effects to development and behaviour. In this study, we tested the effects of a 96 h exposure during embryonic development of marsh frog’s tadpoles to three ecologically relevant Roundup® Power 2.0 concentrations. As expected, given the low concentrations tested, no mortality was observed. Morphological measurements highlighted a reduction in the total length in tadpoles exposed to 7.6 mg a.e./L, while an increase was observed at lower concentrations of 0.7 and 3.1 mg a.e./L compared to control group. Tadpoles raised in 7.6 mg a.e./L also showed a smaller tail membrane than those raised in the control solution. Regarding behaviour, we tested tadpoles in two different sessions (Gosner stages 25 and 28/29) for lateralization, antipredator response and basal activity. Lower intensity of lateralization was detected in tadpoles raised at the highest Roundup® concentration in the first session of observation, while no significant difference among treatments was observed in the second one. In both sessions, effects of Roundup® Power 2.0 embryonic exposure on antipredator response, measured as the proportional change in activity after the injection of tadpole-fed predator (Anax imperator) cue, were not detected. Tadpoles exposed during embryonic development to Roundup® exhibited lower basal activity than the control group, with the strongest reduction for the 7.6 mg a.e./L treatment. Our results reinforce the concern of Roundup® contamination impact on amphibians.

Plastic pollution represents one of the most salient indicators of society’s impact on the environment. The microplastic component of this is ubiquitous, however, microplastic studies are seldom representative of the locations they sample. Over 12 months we explored spatiotemporal variation in microplastic prevalence across a freshwater system and in atmospheric deposition within its catchment, in one of the most temporally comprehensive studies of microplastic pollution. Microplastics were quantified in low concentrations (max 0.4 particles L⁻¹) at all freshwater sites, including upstream of urban areas, and on rivers that do not receive wastewater treatment plant effluent. Extrapolated microplastic abundances at each site varied by up to 8 orders of magnitude over the course of the sampling campaign, suggesting that microplastic surveys that do not account for temporal variability misrepresent microplastic prevalence. Whilst we do not wish to underplay the potential impacts of microplastic particles in the environment, we argue that microplastic pollution needs to be placed in a more critical context, including assessment of temporal variability, to appropriately inform legislators and consumers.

The aquatic ecosystem is seriously damaged because of the heavy use of pesticides and antibiotics. Fish is the indispensable link between environmental pollution and human health. However, the toxic effects of environment-related concentrations of pesticides and antibiotics in fish have not been thoroughly studied. In this study, grass carps exposed to cypermethrin (CMN, 0.651 μg/L) or/and sulfamethoxazole (SMZ, 0.3 μg/L) for 42 days caused oxidative stress, apoptosis and immunodeficiency in the spleen of grass carps. CMN or/and SMZ exposure led to oxidative damage (consumption of antioxidant enzymes (superoxide dismutase and catalase)) and lipid peroxidation (accumulation of malondialdehyde), induced apoptosis (increases in TUNEL index, Bax/bcl-2, p53, puma and Caspase family expression). In addition, the levels of immunoglobulin M (IgM), complement 3 (C3) were significantly decreased in all treatment groups, which trend was also found in C-reactive protein in CMN and MIX group, and lysozyme in MIX group. Transcription of almost all genes involved in the Toll-like receptors (TLR) signaling pathway was up-regulated under CMN or/and SMZ exposure. However, when subsequently attacked by Aeromonas hydrophila for 2 days, the TLR pathway was inhibited in spleens of all treatment groups accompanied by higher mortality. Overall, the environmentally relevant concentration of CMN and SMZ damages the immune system, triggering oxidative stress and apoptosis in carps. And by affecting the conduction of TLR signaling pathway, CMN or/and SMZ exposure inhibits the innate immune response of fish and reducing their disease resistance. This study highlights the importance of rational and regulated use of these pesticides and antibiotics.

The effects of warming and elevated ozone (O₃) concentrations on nitrous oxide (N₂O) emission from cropland has received increasing attention; however, the small number of studies on this topic impedes understanding. A field experiment was performed to explore the role of warming and elevated O₃ concentrations on N₂O emission from wheat-soybean rotation cropland from 2012 to 2013 using open-top chambers (OTCs). Experimental treatments included ambient temperature (control), elevated temperature (+2 °C), elevated O₃ (100 ppb), and combined elevated temperature (+2 °C) and O₃ (100 ppb). Results demonstrate that warming significantly increased the accumulative amount of N₂O (AAN) emitted from the soil-winter wheat system due to enhanced nitrification rates in the wheat farmland and nitrate reductase activity in wheat leaves. However, elevated O₃ concentrations significantly decreased AAN emission from the soil-soybean system owing to reduced nitrification rates in the soybean farmland. The combined treatment of warming and elevated O₃ inhibited the emission of N₂O from the soybean farmland. Additionally, both the warming and combined treatments significantly increased soil nitrification rates in winter wheat and soybean croplands and decreased denitrification rates in the winter wheat cropping system. Our results suggest that global warming and elevated O₃ concentrations will strongly affect N₂O emission from wheat-soybean rotation croplands.

Chronic exposure to environment noise is associated with sleep disturbance and cardiovascular diseases. Assessment of population exposed to environmental noise is limited by a lack of routine noise sampling and is critical for controlling exposure and mitigating adverse health effects. Land use regression (LUR) model is newly applied in estimating environmental exposures to noise. Machine-learning approaches offer opportunities to improve the noise estimations from LUR model. In this study, we employed random forests (RF) model to estimate environmental noise levels in five Canadian cities and compared noise estimations between RF and LUR models. A total of 729 measurements and 33 built environment-related variables were used to estimate spatial variation in environmental noise at the global (multi-city) and local (individual city) scales. Leave one out cross-validation suggested that noise estimates derived from the RF global model explained a greater proportion of variation (R2: RF = 0.58, LUR = 0.47) with lower root mean squared errors (RF = 4.44 dB(A), LUR = 4.99 dB(A)). The cross-validation also indicated the RF models had better general performance than the LUR models at the city scale. By applying the global models to estimate noise levels at the postal code level, we found noise levels were higher in Montreal and Longueuil than in other major Canadian cities.

Topsoils near active and abandoned mining and smelting sites are highly polluted by metal(loid) contaminants, which are often bound to particulates emitted from ore processing facilities and/or windblown from waste disposal sites. To quantitatively determine the contaminant partitioning in the soil particulates, we tested an automated mineralogy approach on the heavy mineral fraction extracted from the mining- and smelting-polluted topsoils exhibiting up to 1920 mg/kg As, 5840 mg/kg Cu, 4880 mg/kg Pb and 3310 mg/kg Zn. A new generation of automated scanning electron microscopy (autoSEM) was combined and optimized with conventional mineralogical techniques (XRD, SEM/EDS, EPMA). Parallel digestions and bulk chemical analyses were used as an independent control of the autoSEM-calculated concentrations of the key elements. This method provides faster data acquisition, the full integration of the quantitative EDS data and better detection limits for the elements of interest. We found that As was mainly bound to the apatite group minerals, slag glass and metal arsenates. Copper was predominantly hosted by the sulfides/sulfosalts and the Cu-bearing secondary carbonates. The deportment of Pb is relatively complex: slag glass, Fe and Mn (oxyhydr)oxides, metal arsenates/vanadates and cerussite were the most important carriers for Pb. Zinc is mainly bound to the slag glass, Fe (oxyhydr)oxides, smithsonite and sphalerite. Limitations exist for the less abundant contaminants, which cannot be fully quantified by autoSEM due to spectral overlaps with some major elements (e.g., Sb vs. Ca, Cd vs. K and Ca in the studied soils). AutoSEM was found to be a useful tool for the determination of the modal phase distribution and element partitioning in the metal(loid)-bearing soil particulates and will definitely find more applications in environmental soil sciences in the future.

Copper is known to interfere with fish olfaction. Although the chemosensory detection and olfactory toxicity of copper ions (Cu²⁺) has been heavily studied in fish, the olfactory-driven detection of copper nanoparticles (CuNPs)—a rapidly emerging contaminant to aquatic systems—remains largely unknown. This study aimed to investigate the olfactory response of rainbow trout to equitoxic concentrations of CuNPs or Cu²⁺ using electro-olfactography (EOG, a neurophysiological technique) and olfactory-mediated behavioural assay. In the first experiment, the concentration of contaminants known to impair olfaction by 20% over 24 h (EOG-based 24-h IC20s of 220 and 3.5 μg/L for CuNPs and Cu²⁺, respectively) were tested as olfactory stimuli using both neurophysiological and behavioural assays. In the second experiment, to determine whether the presence of CuNPs or Cu²⁺ can affect the ability of fish to perceive a social cue (taurocholic acid (TCA)), fish were acutely exposed to one form of Cu-contaminants (approximately 15 min). Following exposure, olfactory sensitivity was measured by EOG and olfactory-mediated behaviour within a choice maze was recorded in the presence of TCA. Results of neurophysiological and behavioural experiments demonstrate that rainbow trout can detect and avoid the IC20 of CuNPs. The IC20 of Cu²⁺ was below the olfactory detection threshold of rainbow trout, as such, fish did not avoid Cu²⁺. The high sensitivity of behavioural endpoints revealed a lack of aversion response to TCA in CuNP-exposed fish, despite this change not being present utilizing EOG. The reduced response to TCA during the brief exposure to CuNPs may be a result of either olfactory fatigue or blockage of olfactory sensory neurons (OSNs) by CuNPs. The observed behavioural interference caused by CuNP exposure may indicate that CuNPs have the ability to interfere with other behaviours potentially affecting fitness and survival. Our findings also revealed the differential response of OSNs to CuNPs and Cu²⁺.