Bauxite extraction by-products (red mud) were used to evaluate their potential ability to stabilize trace elements from dredged and aerated/humidified marine sediment. The investigated by-products were: bauxaline®(BX) that is a press-filtered red mud; bauxsol™(BS) that is a press-filtered red mud previously washed with excess of seawater, and gypsum neutralized bauxaline® (GBX). These materials were separately mixed to dredged composted sediment sample considering 5% and 20% sediment: stabilizer ratios. For pilot experiments, rainfall events were regularly simulated for 3 months. Concentrations of As, Mo, Cd, Cr, Zn, Cu, and Ni were analyzed in collected leachates as well as toxicity. Results showed that Cd, Mo, Zn, and Cu were efficiently stabilized in the solid matrix when 20% of BX, BS, and GBX was applied. Consequently, toxicity of leachates was lower than for the untreated sediment, meaning that contaminants mobility was reduced. A 5% GBX was also efficient for Mo, Zn and Cu stabilization. In all scenarios, As stabilization was not improved. Compared to all other monitored elements, Mo mobility seemed to depend upon temperature-humidity conditions during pilot experiments suggesting the need of further investigations.

The use of road deicing salts in regions that experience cold winters is increasing the salinity of freshwater ecosystems, which threatens freshwater resources. Yet, the impacts of environmentally relevant road salt concentrations on freshwater organisms are not well understood, particularly in stream ecosystems where salinization is most severe. We tested the impacts of deicing salts—sodium chloride (NaCl), magnesium chloride (MgCl2), and calcium chloride (CaCl2)—on the growth and development of newly hatched rainbow trout (Oncorhynchus mykiss). We exposed rainbow trout to a wide range of environmentally relevant chloride concentrations (25, 230, 860, 1500, and 3000 mg Cl− L−1) over an ecologically relevant time period (25 d). We found that the deicing salts studied had distinct effects. MgCl2 did not affect rainbow trout growth at any concentration. NaCl had no effects at the lowest three concentrations, but rainbow trout length was reduced by 9% and mass by 27% at 3000 mg Cl− L−1. CaCl2 affected rainbow trout growth at 860 mg Cl− L−1 (5% reduced length; 16% reduced mass) and these effects became larger at higher concentrations (11% reduced length; 31% reduced mass). None of the deicing salts affected rainbow trout development. At sub-lethal and environmentally relevant concentrations, our results do not support the paradigm that MgCl2 is the most toxic deicing salt to fish, perhaps due to hydration effects on the Mg2+ cation. Our results do suggest different pathways for lethal and sub-lethal effects of road salts. Scaled to the population level, the reduced growth caused by NaCl and CaCl2 at critical early-life stages has the potential to negatively affect salmonid recruitment and population dynamics. Our findings have implications for environmental policy and management strategies that aim to reduce the impacts of salinization on freshwater organisms.

This study presents the occurrence and impact of 78 anticancer drugs compounds in Spanish river basins based on consumption data during the period 2010–2015 and calculation of the predicted environmental concentrations (PEC). The total consumption of anticancer drugs in Spanish pharmacies was of 23.4 tons in 2015, being mycophenolic acid and hydroxycarbamide the drugs with the highest prescription. Their PECs in river at national scale were up to 80 ng/L. However, the use of different dilution factors revealed major differences between hydrographic basins, and PECriver rose up to 68,014 ng/L in highly populated rivers with low flows. Concerning acute toxicity, there was no expected risk for the aquatic environment. However, chronic toxicity tests revealed possible long-term mutagenic effects for aquatic organisms. This study provides the tools for the estimation of PEC at river basin scale using time trend consumption data compilation. This information is very useful for prioritization of compounds of concern and permit to focus resources in environmental monitoring and risk evaluation.

Venlafaxine is an antidepressant drug that has been detected in municipal wastewater effluents at low μg/L concentrations. To assess the potential of this compound to affect the survival, development and reproductive capacity of fish, we exposed fathead minnow (Pimephales promelas) over a full lifecycle in a flow-through system to nominal venlafaxine concentrations of 0.88, 8.8, and 88 μg/L. Mean measured venlafaxine concentrations in these treatments were 1.0, 9.3 and 75 μg/L. During the 167–168 d exposure, no significant changes were observed in survival, or the weights and lengths of fathead minnows. At maturity, there were no significant differences relative to controls in condition factor, liver-somatic index, or secondary sex characteristics in the venlafaxine exposed male or female fish. Fathead minnows from the highest venlafaxine treatment (i.e. 88 μg/L) produced 46% more eggs per female than control fish (p = 0.031). Egg quality, % fertilization, % hatching, and % deformities in F1 fry were unaffected by exposure of the parent fish to venlafaxine at any of the test concentrations. Venlafaxine exposure at environmentally relevant concentrations (i.e. 0.88 and 8.8 μg/L) caused no adverse effects in fathead minnows. This study is the first to assess the potential for effects in fish exposed to the antidepressant venlafaxine over a full lifecycle.

Understanding the colloidal stability of graphene is essential for predicting its transport and ecological risks in aquatic environments. We investigated the agglomeration of ¹⁴C-labeled few-layer graphene (FLG) at concentrations spanning nearly four orders of magnitude (2 μg/L to 10 mg/L) using dynamic light scattering and sedimentation measurements. FLG agglomerates formed rapidly in deionized water at concentrations >3 mg/L. From 1 mg/L to 3 mg/L, salt-induced agglomeration was decreased with dilution of FLG suspensions; the critical coagulation concentration of the more concentrated suspension (3 mg/L) was significantly lower than the dilute suspension (1 mg/L) in the presence of NaCl (1.6 mmol/L and 10 mmol/L, respectively). In contrast, FLG underwent slow agglomeration and settling at concentrations ≤0.1 mg/L in NaCl solutions and ambient waters with low ionic strength (<10 mmol/L). FLG nanoparticles with smaller lateral sizes (25 nm–75 nm) were shown to agglomerate more slowly than larger FLG, and these small FLG particles exhibited greater bioaccumulation in zebrafish embryo and stronger chorion penetration ability than larger FLG particles. These findings suggest that FLG at more environmentally relevant concentration is relatively stable and may have implications for exposure of small FLG to ecological receptors.

Calanoid copepods play an important role in the functioning of marine and brackish ecosystems. Information is scarce on the behavioral toxicity of engineered nanoparticles to these abundant planktonic organisms. We assessed the effects of short-term exposure to nonfunctionalized gold nanoparticles on the swimming behavior of the widespread estuarine copepod Eurytemora affinis. By means of three-dimensional particle tracking velocimetry, we reconstructed the trajectories of males, ovigerous and non-ovigerous females. We quantified changes in their swimming activity and in the kinematics and geometrical properties of their motion, three important descriptors of the motility patterns of zooplankters. In females, exposure to gold nanoparticles in suspension (11.4 μg L−1) for 30 min caused depressed activity and lower velocity and acceleration, whereas the same exposure caused minimal effects in males. This response differs clearly from the hyperactive behavior that is commonly observed in zooplankters exposed to pollutants, and from the generally lower sensitivity of female copepods to toxicants. Accumulation of gold nanoparticles on the external appendages was not observed, precluding mechanical effects. Only very few nanoparticles appeared sporadically in the inner part of the gut in some samples, either as aggregates or as isolated nanoparticles, which does not suggest systemic toxicity resulting from pronounced ingestion. Hence, the precise mechanisms underlying the behavioral toxicity observed here remain to be elucidated. These results demonstrate that gold nanoparticles can induce marked behavioral alterations at very low concentration and short exposure duration. They illustrate the applicability of swimming behavior as a suitable and sensitive endpoint for investigating the toxicity of nanomaterials present in estuarine and marine environments. Changes in swimming behavior may impair the ability of planktonic copepods to interact with their environment and with other organisms, with possible impacts on population dynamics and community structure.

Current risk assessment models for metals such as the biotic ligand model (BLM) are usually applied to individual metals, yet toxic metals are rarely found singly in the environment. In the present research, the toxicity of Cu and Zn alone and together were studied in wheat (Triticum aestivum L.) using different Ca2+ and Mg2+ concentrations, pH levels and Zn:Cu concentration ratios. The aim of the study was to better understand the toxicity effects of these two metals using BLMs and toxic units (TUs) from single and combined metal toxicity data. The results of single-metal toxicity tests showed that toxicity of Cu and Zn tended to decrease with increasing Ca2+ or Mg2+ concentrations, and that the effects of pH on Cu and Zn toxicity were related not only to free Cu2+ and Zn2+ activity, respectively, but also to other inorganic metal complex species. For the metal mixture, Cu–Zn interactions based on free ion activities were primarily additive for the different Ca2+ and Mg2+ concentrations and levels of pH. The toxicity data of individual metals derived by the BLM, which incorporated Ca2+ and Mg2+ competition and toxicity of inorganic metal complexes in a single-metal toxicity assessment, could predict the combined toxicity as a function of TU. There was good performance between the predicted and observed effects (root mean square error [RMSE] = 7.15, R2 = 0.97) compared to that using a TU method with a model based on free ion activity (RMSE = 14.29, R2 = 0.86). The overall findings indicated that bioavailability models that include those biochemistry processes may accurately predict the toxicity of metal mixtures.

The potential impacts of environmentally accumulated zinc oxide nanoparticles (nZnOs) on plant growth have not been well studied. A transcriptome profile analysis of maize exposed to nZnOs showed that the genes in the shoots and roots responded differently. Although the number of differentially expressed genes (DEGs) in the roots was greater than that in the shoots, the number of up- or down-regulated genes in both the shoots and roots was similar. The enrichment of gene ontology (GO) terms was also significantly different in the shoots and roots. The “nitrogen compound metabolism” and “cellular component” terms were specifically and highly up-regulated in the nZnO-exposed roots, whereas the categories “cellular metabolic process”, “primary metabolic process” and “secondary metabolic process” were down-regulated in the exposed roots only. Our results revealed the DEG response patterns in maize shoots and roots after nZnO exposure.

Bromide is a conservative tracer that is often applied with non-conservative solutes such as pesticides to estimate their retardation in the soil. It has been applied in concentrations of up to 250 g Br L−1, levels at which the growth of single-celled organisms can be inhibited. Bromide applications may therefore affect the biodegradation of non-conservative solutes in soil.The present study investigated the effect of potassium bromide (KBr) on the mineralisation of three pesticides – glyphosate, MCPA and metribuzin – in four agricultural A-horizon soils. KBr was added to soil microcosms at concentrations of 0, 0.5, 2.5 and 5 g Br− L−1 in the soil solution. The study concluded that KBr had a negative effect on pesticide mineralisation. The inhibitory effect varied depending on the KBr concentration, the type of pesticide and the type of soil. Furthermore, 16 S amplicon sequencing revealed that the KBr treatment generally reduced the abundance of bacteroidetes and proteobacteria on both an RNA and DNA level.Therefore, in order to reduce the effect of KBr on the soil bacterial community and consequently also on xenobiotic degradation, it is recommended that KBr be applied in a concentration that does not exceed 0.5 g Br− L−1 in the soil water.

The Ordos region of Inner Mongolia is rapidly developing and suffers from poor air quality and unhealthy levels of fine particulate matter. PM2.5 concentrations in the Ordos region were found to exceed 75 μg/m3 on average, annually, with peak pollution days in excess of 350 μg/m3, but local air pollution emissions from surrounding sources are not sufficient to drive pollution levels to these concentrations. The current study was designed to quantify sources of PM2.5 and assess the local source contributions and effects of regional transport on local pollution. The results show that the Ordos region is primarily impacted by regional long-range transport of pollutants from anthropogenic sources located outside of the Inner Mongolia in Shanxi province areas but is also largely affected by regional dust transported from the deserts located in western Inner Mongolia. The analysis proved that approximately 77% of PM2.5 mass is transported long-range from the sites exterior to the study area and contributes 59.32 μg/m3 on average, annually, while the local sources contribute 17.41 μg/m3 (23%) on annual average to the PM2.5 mass in the study area. High spatial correlation coefficients (R2 > 0.6) were observed for most of the factors pointing to the transport of external emissions into the area. Spatial correlation analysis, bivariate polar plots and hybrid trajectory models for industrial and secondary inorganic factors provide evidence for the impact of long-range transport from Shanxi province areas. In addition, the deserts in western Inner Mongolia were found to be the source regions for dust. Finally, our analysis shows that the source of oil combustion and mobile factors are impacted by local sources in the Ordos region; however, some regional impacts from other regions were also observed for mobile source in the area.