The ubiquity of microplastics in the world's ocean has aroused great concern. However, the ecological effects of microplastics at environmentally realistic concentrations are unclear. Here we showed that exposure of marine medaka (Oryzias melastigma) to environmentally relevant concentrations of 10 μm polystyrene microplastics for 60 days not only led to microplastic accumulation in the gill, intestine, and liver, but also caused oxidative stress and histological changes. Moreover, 2, 20, and 200 μg/L microplastics delayed gonad maturation and decreased the fecundity of female fish. Alterations of the hypothalamus-pituitary-gonadal (HPG) axis were investigated to reveal the underlying mechanisms, and gene transcription analysis showed that microplastic exposure had significantly negative regulatory effects in female HPG axis. Transcription of genes involved in the steroidogenesis pathway in females were also downregulated. This disruption resulted in decreased concentrations of 17β-estradiol (E₂) and testosterone (T) in female plasma. Furthermore, parental exposure to 20 μg/L microplastics postponed the incubation time and decreased the hatching rate, heart rate, and body length of the offspring. Overall, the present study demonstrated for the first time that environmentally relevant concentrations of microplastics had adverse effects on the reproduction of marine medaka and might pose a potential threat to marine fish populations.

Muzzle emissions from firing an M4 carbine rifle in a semi-enclosed chamber were characterized for an array of compounds to provide quantitative data for future studies on potential inhalation exposure and rangeland contamination. Air emissions were characterized for particulate matter (PM) size distribution, composition, and morphology; carbon monoxide (CO); carbon dioxide (CO₂); energetics; metals; polycyclic aromatic hydrocarbons; and methane. Three types of ammunition were used: a “Legacy” (Vietnam-era) round, the common M855 round (no longer fielded), and its variant, an M855 round with added potassium (K)-based salts to reduce muzzle flash. Average CO concentrations up to 1500 ppm significantly exceeded CO₂ concentrations. Emitted particles were in the respirable size range with mass median diameters between 0.33 and 0.58 μm. PM emissions were highest from the M855 salt-added ammunition, likely due to incomplete secondary combustion in the muzzle blast caused by scavenging of combustion radicals by the K salt. Copper (Cu) had the highest emitted metal concentration for all three round formulations, likely originating from the Cu jacket on the bullet. Based on a mass balance analysis of each round's formulation, lead (Pb) was completely emitted for all three round types. This work demonstrated methods for characterizing emissions from gun firing which can distinguish between round-specific effects and can be used to initiate studies of inhalation risk and environmental deposition.

Oxygenated polycyclic aromatic hydrocarbons (oxy-PAHs) are a group of environmental pollutants found in complex mixtures together with PAHs. In contrast to the extensively studied PAHs, which have been established to have mutagenic and carcinogenic properties, much less is known about the effects of oxy-PAHs. The present work aimed to investigate the genotoxic potency of a set of environmentally relevant oxy-PAHs along with environmental soil samples in human bronchial epithelial cells (HBEC). We found that all oxy-PAHs tested induced DNA strand breaks in a dose-dependent manner and some of the oxy-PAHs further induced micronuclei formation. Our results showed weak effects in response to the oxy-PAH containing subfraction of the soil sample. The genotoxic potency was confirmed in both HBEC and HepG2 cells following exposure to oxy-PAHs by an increased level of phospho-Chk1, a biomarker used to estimate the carcinogenic potency of PAHs in vitro. We further exposed zebrafish embryos to single oxy-PAHs or a binary mixture with PAH benzo[a]pyrene (B[a]P) and found the mixture to induce comparable or greater effects on the induction of DNA strand breaks compared to the sum of that induced by B[a]P and oxy-PAHs alone. In conclusion, oxy-PAHs were found to elicit genotoxic effects at similar or higher levels to that of B[a]P which indicates that oxy-PAHs may contribute significantly to the total carcinogenic potency of environmental PAH mixtures. This emphasizes further investigations of these compounds as well as the need to include oxy-PAHs in environmental monitoring programs in order to improve health risk assessment.

Phytostabilization of sulfidic PbZn tailing landscapes may be one of interim options of tailings management, but which is limited by acute phytotoxicity of heavy metals in the tailings. The present study aimed to investigate the effectiveness of soluble phosphate (i.e., K2HPO4) in immobilizing soluble Pb, Cd and Zn and lowering their acute phytotoxicity. The addition of soluble phosphate improved the growth of native plants Acacia chisholmii and survival rate of A. ligulata, where the latter exhibited 100% survival rate. This was in contrast to effects of conventional organic amendment in the tailings on metal solubility (e.g., elevated metal levels in porewater) and plant survival (e.g., only 42%). Organic amendment with mulch did not lower the levels of water-soluble Cd, Pb and Zn and their concentrations in plant tissues after 56 days of plant growth in the treatment. In contrast, the tailings amended with K2HPO4 significantly decreased metal concentrations in the porewater and plant tissues by about 80–92% and 56–88%, respectively. The metal immobilization by phosphate was due to the formation of insoluble or sparingly soluble metal (Pb, Cd and Zn)-phosphate minerals in the tailings with circumneutral pH conditions, as revealed by using X-ray diffraction and scanning electron microanalyses. The reduced metal concentrations in roots and shoots of Acacia species after direct root contact with the K2HPO4 amended tailings suggested that metals (i.e., Pb, Cd and Zn) were effectively immobilized by the phosphate treatment of the tailings. These findings indicate that addition of high dosage of soluble phosphate may provide a low cost option to treat sulfidic PbZn tailings for rapid phytostabilization of the tailings surface, as an interim option to manage environmental risks of sulfidic PbZn tailings.

Baseline emission values of greenhouse gases were not well established for commercial poultry barns in cold regions, including Canada, due to a lack of well-designed field studies. Emission factors of carbon dioxide (CO₂), methane (CH₄), and nitrous oxide (N₂O), were acquired for a commercial broiler barn and cage-layer barn in the Canadian Prairies climate. Between March 2015 and February 2016, monthly measurements throughout the year for the layer barn and over 6 flocks for the broiler barn, and diurnal measurements in the mild, warm, and cold seasons for both barns were conducted, respectively. The ventilation rate was estimated based on a CO₂ mass balance method; thus CO₂ emissions were quantified by the CIGR (2002) models. The CH₄ and N₂O emissions present at low levels from global perspective for both barns; the cold climate proved to be a major reason for the lower CH₄ emission from the layer barn. Considerable seasonal effect was observed only for N₂O emissions from the broiler barn, and for CH₄ and N₂O emissions from the layer barn, both with higher emissions in the mild and warm seasons than in the cold season. The big diurnal variations of CO₂ emissions for the layer barn demonstrated the uncertainty of the seasonal results by snapshot measurements and correction factors (from −20.9% to −22.5%) were obtained. Besides, the difference of CH₄ and N₂O concentrations and emissions as well as CO₂ concentrations between best-case (the first day after manure removal) and worst-case conditions (the last day before manure removal) was not obvious for the layer barn. Additionally, changes of temperature and ventilation rate were likely to have more impact on N₂O emission for the broiler barn and more impact on CH₄ emission for the layer barn than on the other two gas emissions, both with positive correlations.

Predicting the translocation of organic contaminants to plants is crucial to ensure the quality of agricultural goods and assess the risk of human exposure through the food web. In this study, the performance of a modified plant uptake model was evaluated considering a number of chemicals, such as polycyclic aromatic hydrocarbons (PAHs), organochlorine pesticides (OCPs) and polybrominated diphenyl ethers (PBDEs), with a range of physicochemical properties; different plant species (Ipomoea aquatica Forsk (swamp morning glory), Chrysanthemum coronarium L. (crown daisy), Zea mays L. (corn), Brassica rapa pekinensis (Chinese cabbage), Cucurbita moschata (pumpkin), Raphanus sativus L. (radish), Spinacia oleracea L. (spinach) and Capsicum annuum L. (pepper)); and different types of soil (paddy soil, laterite soil and black soil). The biases of predictions from a previously used partition-limited model were −76.4% to −99.9% relative to the measured concentrations. An overall transmission factor (αtf=0.39), calculated from a linear regression of the measured bioavailable fraction (Cbᵢₒ) and the total concentration in plants, was considered a crucial modification and was included in the modified model. Cbᵢₒ was found to better represent the chemical content available in soil for root uptake. The results from this study improve the accuracy of predictions for vegetation-uptake assessments by modifying the partition-limited model and then validating the modified model using comparisons between predicted data and measured values. The accuracy of the concentrations of organic contaminants in plants improved: when using the modified model, 89.5% of the predictions were within 40% of the actual value. The average bias was limited to 1.5%–30.5%. The model showed great potential to predict plant uptake using the bioavailable fraction concentration in soil.

While several mechanisms may explain metal-related health effects, the exact cellular processes are not fully understood. We evaluated the association between leukocyte telomere length (LTL) and urine arsenic (ΣAs), cadmium (Cd) and tungsten (W) exposure in the Strong Heart Study (SHS, N = 1702) and in the Strong Heart Family Study (SHFS, N = 1793).Urine metal concentrations were measured using ICP-MS. Arsenic exposure was assessed as the sum of inorganic arsenic, monomethylarsonate and dimethylarsinate levels (ΣAs). LTL was measured by quantitative polymerase chain reaction.In the SHS, median levels were 1.09 for LTL, and 8.8, 1.01 and 0.11 μg/g creatinine for ΣAs, Cd, and W, respectively. In the SHFS, median levels were 1.01 for LTL, and 4.3, 0.44, and 0.10 μg/g creatinine. Among SHS participants, increased urine ΣAs, Cd, and W was associated with shorter LTL. The adjusted geometric mean ratio (95% confidence interval) of LTL per an increase equal to the difference between the percentiles 90th and 10th in metal distributions was 0.85 (0.79, 0.92) for ΣAs, 0.91 (0.84, 1.00) for Cd and 0.93 (0.88, 0.98) for W. We observed no significant associations among SHFS participants. The findings also suggest that the association between arsenic and LTL might be differential depending on the exposure levels or age.Additional research is needed to confirm the association between metal exposures and telomere length.

Knowledge of the transport and fate of pathogenic Escherichia coli, especially in the areas contaminated with crude oil, is required to assess contamination of shallow groundwater resources. The present study aims to investigate the effect of crude oil-mediated water repellency on the movement of nalidixic acid-resistant Escherichia coli strain (E. coli NAR) and bromide (Br) as an inert tracer in two soil types. The soils were contaminated at three levels of 0, 0.5 and 1% w/w of total petroleum hydrocarbons (TPHs) using crude oil. Steady-state saturated flow in the soil columns was controlled using a tension infiltrometer. Leaching experiments were conducted through the columns of repacked (un-weathered) and physically-weathered clay loam (CL) and sandy loam (SL) soils. The columns leachate was sampled at specific times for 4 pore volumes. The shape of breakthrough curves for the E. coli NAR and Br depended on soil texture and structure and the TPHs level. Preferential flow in the crude oil-mediated water-repellent soils facilitated the transport of contaminants especially E. coli NAR. Filtration coefficient and relative adsorption index of bacteria were greatest in the repacked CL soils and were lowest in the weathered SL soils. Discontinuity of soil pores and lower flow velocity resulted in greater filtration of E. coli NAR in the repacked CL soil than other treatments. Physical weathering induced the formation of aggregates which reduced soil particle surfaces available for retention of water-repellent oil and contaminants. Movement of both bacteria and Br tracer in the weathered SL soil with 1% TPHs was higher than other treatments. This finding was attributed to low specific surface area, continuity of the pores and water repellency-mediated preferential pathways in the weathered SL soil columns. Our findings implied that shallow groundwater resources could be very sensitive to microbial contamination particularly in the oil-mediated water-repellent soils.

Hexabromocyclododecanes (HBCDDs) are common chemical additives in expanded polystyrene foam (EPS). To evaluate the bioaccumulation potential of endogenous HBCDDs in EPS microparticles by earthworms, two ecologically different species of earthworms (Eisenia fetida and Metaphire guillelmi) were exposed to soil added with EPS microparticles of different particle sizes (EPS2000, 830–2000 μm and EPS830, <830 μm). To clarify the accumulation mechanisms, leaching experiments using EPS microparticles in different solutions were conducted. After exposure to EPS microparticles-amended soils (S-EPS) for 28 d, the total concentrations of HBCDDs reached 307–371 ng g−1 dw in E. fetida and 90–133 ng g−1 dw in M. guillelmi, which were higher than those in earthworms exposed to the soil that was artificially contaminated with a similar level of HBCDDs directly (ACS). The accumulation of HBCDDs in earthworms was significantly influenced by EPS microparticles' size and earthworms' species. The total concentrations of HBCDDs in earthworms' cast were significantly higher than the theoretical concentration of HBCDDs in S-EPS, which suggested that EPS microparticles can be ingested by earthworms. The release rate of HBCDDs from EPS5000 (2000–5000 μm) into water-based solutions (<1%) after a 3.5-h incubation was far lower than that into earthworm digestive fluid (7%). These results illustrated that the ingestion of EPS microparticles and consequent solubilization of HBCDDs by digestive fluid play an important role in the accumulation of HBCDDs contained in EPS microparticles in earthworms. After a 28-d incubation with the soil solution, 4.9% of the HBCDDs was accumulatively leached from the EPS5000, which indicated that HBCDDs can be released from EPS microparticles to soil environment, and then accumulated by earthworms. Moreover, similar to those exposed to ACS, the diastereoisomer- and enantiomer-specific accumulation of HBCDDs in earthworms occurred when exposed to S-EPS. This study provides more evidence for the risk of microplastics to the soil ecosystem.

In this study, graphene aerogel (GA) was successfully prepared through a simple hydrothermal method. The resulting GA exhibited a porous network structure with a large specific surface area (350.8 m²/g), ultra-light mass and easy separation from water. The pHIEP value of the GA was estimated to be 3.5. The adsorption process and the factors that affect adsorption capacity were studied. The adsorption could be conducted in a wide pH range from 2.0 to 7.0. The maximum adsorption capacity of GA towards U(VI) at pH 4.0 and T = 298 K was 238.67 mg/g calculated from the Langmuir model. The GA had greatly rapid adsorption property for the removal of U(VI) at pH 4.0. Kinetic data showed good correlation with pseudo-second-order equation. Fourier transform infrared spectroscopy and X-ray photoelectron spectrometry characterizations showed that GA adsorbed U(VI) through chemical interaction by oxygen-containing and nitrogen-containing groups functional groups. The results show that GA has excellent application potential as an adsorbent material for removing U(VI) from aqueous solution.