Phosphogypsum (PG) is disposed worldwide in large stacks usually placed in coastal zones, as in the case of Huelva (SW of Spain), where around 100 Mt of PG are stored on the salt marshes of the Tinto River estuary covering a surface of about 1000 ha. This management generates the weathering of PG, and due to its high acidity (pH ≈ 2) and pollutant load can provoke significant emissions into their surroundings. In this work were evaluated by laboratory experiments the effects of pH increase in the behaviour of heavy metals and natural radionuclides during the mixing of phosphogypsum leachates with seawater.The acidic phosphogypsum leachates showed concentrations of heavy metals from two to three orders of magnitude higher than natural continental waters, and natural radionuclides (U-isotopes and ²¹⁰Po) from four to five orders of magnitude higher than unperturbed aquatic systems. Major elements and some heavy metals as Mn, Ni, Cd, As, Sb and Co showed a conservative behaviour during the neutralisation of the leachates with seawater, remaining in the liquid phase, while other ones as Al, Fe, Cr, Zn, Cu, Pb precipitated and/or were adsorbed onto the solid phase. The U-isotopes and ²¹⁰Po showed a clear non-conservative behaviour probably due to coprecipitation/adsorption processes onto the formed precipitates, but while ²¹⁰Po reached a total removal at pH ≈ 7, U- isotopes after a total removal at pH ≈ 5 returned into the liquid phase due to redissolution/desorption processes at near neutral pH.The formed precipitates, mainly composed by iron phosphates particles, showed heavy metal and natural radionuclide concentrations from one to three orders of magnitude higher than unperturbed soils. All these facts demonstrate the serious environmental impact produced by the PG stacks into their surroundings and the urgency of effective restoration measures.

Di (2-ethylhexyl) phthalate (DEHP) is a widespread plasticizer that persists in the environment and can significantly contribute to serious health hazards of liver especially oxidative stress injury. Lycopene (LYC) as a carotenoid has recently gained widespread attention because of antioxidant activity. However, the potential mechanism of DEHP-induced hepatotoxicity and antagonism effect of LYC on it are still unclear. To explore the underlying mechanisms of this hypothesis, the mice were given by gavage with LYC (5 mg/kg) and DEHP (500 or 1000 mg/kg). The data suggested that DEHP caused liver enlargement, reduction of antioxidant activity markers, increase of oxidative stress indicators and disorder of cytochrome P450 enzymes system (CYP450s) homeostasis. DEHP-induced reactive oxygen species (ROS) activated the NF-E2-relatedfactor2 (Nrf2) and nuclear xenobiotic receptors (NXRs) system including Aryl hydrocarbon receptor (AHR), Pregnane X receptor (PXR) and Constitutive androstane receptor (CAR). Interestingly, these disorders and injuries were prevented after LYC treatment. Taken together, DEHP administration resulted in hepatotoxicity including oxidative stress injury and disordered CYP450 system, but these alterations might be ameliorated by LYC via crosstalk between AHR–Nrf2 pathway.

Systemic toxicity, particularly, developmental defects of humidifier disinfectant chemicals that have caused lung injuries in Korean children, remains to be elucidated. This study evaluated the mechanisms of the adverse effects of 5-chloro-2-methyl-4-isothiazoline-3-one/2methyl-4-isothiazolin-3-one (CMIT/MIT), one of the main biocides of the Korean tragedy, and identify the most susceptible developmental stage when exposed in early life. To this end, the study was designed to analyze several endpoints (morphology, heart rate, behavior, global DNA methylation, gene expressions of DNA methyl-transferases (dnmts) and protein profiling) in exposed zebrafish (Danio rerio) embryos at various developmental stages. The results showed that CMIT/MIT exposure causes bent tail, pericardial edema, altered heart rates, global DNA hypermethylation and significant alterations in the locomotion behavior. Consistent with the morphological and physiological endpoints, proteomics profiling with bioinformatics analysis suggested that the suppression of cardiac muscle contractions and energy metabolism (oxidative phosphorylation) were possible pivotal underlying mechanisms of the CMIT/MIT mediated adverse effects. Briefly, multi-level endpoint analysis indicated the most susceptible window of exposure to be ≤ 6 hpf followed by ≤ 48 hpf for CMIT/MIT. These results could potentially be translated to a risk assessment of the developmental exposure effects to the humidifier disinfectants.

There is growing evidence of widespread contamination of freshwater ecosystems with microplastics. However, the effects of chronic microplastic ingestion and its interaction with other pollutants and stress factors on the life-history traits and the host-microbiome of aquatic invertebrates are not well understood. This study investigates the effects of exposure to sediment spiked with 1 μm polystyrene-based latex microplastic spheres, an environmentally realistic concentration of a pyrethroid pesticide (esfenvalerate), and a combination of both treatments on the life-history traits of the benthic-dwelling invertebrate, Chironomus riparius and its microbial community. The chironomid larvae were also exposed to two food conditions: abundant or limited food in the sediment, monitored for 28 and 34 days respectively. The microplastics and esfenvalerate had negative effects on adult emergence and survival, and these effects differed between the food level treatments. The microbiome diversity was negatively affected by the exposure to microplastics, while the relative abundances of the four top phyla were significantly affected only in the high food level treatment. Although the combined exposure to microplastics and esfenvalerate showed some negative effects on survival and emergence, there was little evidence for synergistic effects when compared to the single exposure. The food level affected all life-history traits and the microbiota, and lower food levels intensified the negative effects of the exposure to microplastics, esfenvalerate and their combination. We argue that these pollutants can affect crucial life-history traits such as successful metamorphosis and the host-microbiome. Therefore, it should be taken into consideration for toxicological assessment of pollutant acceptability. Our study highlights the importance of investigating possible additive and synergic activities between stressors to understand the effects of pollutants in the life story traits and host-microbiome.

Plastics are globally distributed in oceans and can pose a threat to the environment and organisms. In this study, plastic pollution in surface water and sediments of the Bohai Sea was assessed based on plastic abundance, distribution and characteristics (shape, polymer, size and color). Water and sediment samples were collected across the sea using a plankton net (330 μm) and a grab sampler, respectively. The following conclusions were reached. 1) In surface water, large plastics were less abundant (0.14 items/m³) and showed less diverse characteristics than microplastics (0.79 items/m³) but did not significantly differ in spatial distribution. 2) Microplastics in water were more abundant (1.95 items/m³) with more diverse characteristics in Liaodong Bay than in other regions of the sea (0.26–0.59 items/m³). Plastic waste from highly concentrated agricultural, industrial and fishery activities could make large contributions to microplastics in Liaodong Bay. Additionally, low hydrodynamics and long distance to Bohai Strait are unfavorable for diffusion of particles, facilitating the retention of microplastics and increasing the abundance in this bay. 3) Microplastics in sediments were smaller in terms of dominant sizes (<0.5 mm) with less diverse characteristics than particles in water (0.5–1.5 mm). Specifically, fragments, foams and lines dominated among the microplastics in water, whereas fibers and fragments were dominant particles in sediments; alkyd resin, polyethylene, polystyrene and polypropylene (PP) predominated among the particles in water, but rayon, cellulose and PP were dominant particles in sediments. 4) Neither abundance nor size of microplastics in the two media was proportionally correlated and showed low similarity indexes of polymer (0.16), shape (0.29) or color (0.38). This could be related to mismatch in spatiotemporal distributions and variations in the characteristics, fate and behavior of microplastics in the two media. The findings provide knowledge for tracing the sources of plastics in the Bohai Sea.

The Amazon coastal zone has become contaminated with organic pollutants, such as polycyclic aromatic hydrocarbons (PAHs). However, information about their distribution and sources in this area is scarce, despite increasing deforestation and oil exploitation. Therefore, individual PAHs were analysed in the sediments of the Oyapock estuary, which is located in the Amazon coastal zone. This study provides information about the spatial and short-term temporal distributions of PAHs and discusses the major sources of PAHs to better understand the anthropogenic processes occurring in adjacent areas. The concentrations of all sixteen priority PAHs defined by the US EPA (United States Environmental Protection Agency, ∑₁₆PAHs) ranged from 10.9 to 138.8 ng g⁻¹ with a mean and standard deviation = 37.9 ± 20.5 and indicated that this estuary is not contaminated, while the mean levels were similar to those found in other Amazon regions and pristine areas along the coast of Brazil. No significant differences were found in the sedimentary PAHs levels between the wet and dry sampling campaigns, despite the different climatic conditions. Diagnostic ratios, positive matrix factorization (PMF) and cluster analysis have shown that the majority of the investigated PAHs were derived from combustion processes (at least 55.1%, as estimated by the PMF model). Localized source inputs from oil and its by-products concomitantly with natural/biogenic sources appear to be secondary sources. The PAH contribution from biomass and wood combustion was approximately 13.6% and was relatively lower than other regions of the Amazon that are undergoing massive biomass burning. As the first study of PAHs in this region, this study provides vital information on the healthy state of the estuary and can serve as a baseline for assessing the impacts of acute oil disasters or the chronic input of PAHs as a result of human settlements.

Fish embryos, as an endogenous system, strictly regulate an energy metabolism that is particularly sensitive to environmental pressure. This study used orange-spotted grouper embryos and stable isotope ⁶⁷Zn to test the hypothesis that waterborne Zn exposure had a significant effect on energy metabolism in embryos. The fish embryos were exposed to a gradient level of waterborne ⁶⁷Zn, and then sampled to quantify ⁶⁷Zn bioaccumulation and mRNA expressions of key genes involved glucose metabolism. The results indicated that the bioaccumulated ⁶⁷Zn generally increased with increasing waterborne ⁶⁷Zn concentrations, while it tended to be saturated at waterborne ⁶⁷Zn > 0.7 mg L⁻¹. As we hypothesized, the expression of PK and PFK gene involved glycolysis pathway was significantly up-regulated under waterborne ⁶⁷Zn exposure >4 mg L⁻¹. Waterborne ⁶⁷Zn exposure >2 mg L⁻¹ significantly suppressed PCK and G6PC gene expression involved gluconeogenesis pathway, and also inhibited the AKT2, GSK-3beta and GLUT4 genes involved Akt signaling pathway. Our findings first characterized developmental stage-dependent Zn uptake and genotoxicity in fish embryos. We suggest fish embryos, as a small-scale modeling biosystem, have a large potential and wide applicability for determining cytotoxicity/genotoxicity of waterborne metal in aquatic ecosystem.

The crude e-waste recycling has been regulated in China since the late 2000s; however, information on the recent levels and the ecological risks of e-waste derived contaminants such as halogenated flame retardants (HFRs) in the e-waste sites are limited. We therefore examined the concentrations of several HFRs in wild, prey-sized mud carps collected from a typical e-waste site in 2006, 2011 and 2016, to understand the exposure dynamics and ecological risk of these chemicals. Several ecological and biological parameters including δ¹⁵N, δ¹³C, body size and lipid content of the fish were also examined, to ensure an overall uniformity of the sample set among the sampling years. Among the HFRs measured, polybrominated diphenyl ethers (PBDEs) were detected at the highest concentrations (contributing >90% to ∑HFRs), followed by Dechlorane Plus (DPs), polybrominated biphenyls (PBBs), and alternative brominated flame retardants (ABFRs). The fish concentrations of ∑PBDEs, ∑PBBs and ∑DPs significantly dropped by 65%, 57% and 53% from 2006 to 2011, and 12%, 74% and 51% from 2011 to 2016, respectively; likely reflecting the positive impact of the environmental regulations on crude e-waste recycling. The ∑ABFRs concentrations were also decreased by 80% from 2006 to 2011, but increased by 127% from 2011 to 2016; suggesting possible fresh input of these novel HFRs in recent years. In addition to the changes in the HFR concentrations, contaminant profiles in the fish were also changed, possibly due to environmental degradation of the HFRs. Despite our conservative method of risk assessment, we found that PBDEs posed an important risk both for the mud carp and for piscivorous wildlife that inhabit the e-waste site.

Low-cost air quality sensors can help increase spatial and temporal resolution of air pollution exposure measurements. These sensors, however, most often produce data of lower accuracy than higher-end instruments. In this study, we investigated linear and random forest models to correct PM₂.₅ measurements from the Denver Department of Public Health and Environment (DDPHE)’s network of low-cost sensors against measurements from co-located U.S. Environmental Protection Agency Federal Equivalence Method (FEM) monitors. Our training set included data from five DDPHE sensors from August 2018 through May 2019. Our testing set included data from two newly deployed DDPHE sensors from September 2019 through mid-December 2019. In addition to PM₂.₅, temperature, and relative humidity from the low-cost sensors, we explored using additional temporal and spatial variables to capture unexplained variability in sensor measurements. We evaluated results using spatial and temporal cross-validation techniques. For the long-term dataset, a random forest model with all time-varying covariates and length of arterial roads within 500 m was the most accurate (testing RMSE = 2.9 μg/m³ and R² = 0.75; leave-one-location-out (LOLO)-validation metrics on the training set: RMSE = 2.2 μg/m³ and R² = 0.93). For on-the-fly correction, we found that a multiple linear regression model using the past eight weeks of low-cost sensor PM₂.₅, temperature, and humidity data plus a near-highway indicator predicted each new week of data best (testing RMSE = 3.1 μg/m³ and R² = 0.78; LOLO-validation metrics on the training set: RMSE = 2.3 μg/m³ and R² = 0.90). The statistical methods detailed here will be used to correct low-cost sensor measurements to better understand PM₂.₅ pollution within the city of Denver. This work can also guide similar implementations in other municipalities by highlighting the improved accuracy from inclusion of variables other than temperature and relative humidity to improve accuracy of low-cost sensor PM₂.₅ data.

The effects of biological activated carbon treatment using Fe₂O₃ modified coconut shell-based activated carbon (Fe/CAC) were investigated on the occurrence of opportunistic pathogens (OPs) and formation of disinfection by-products (DBPs) in simulated drinking water distribution systems (DWDSs) with unmodified CAC as a reference. In the effluent of annular reactor (AR) with Fe/CAC, the OPs growth and DBPs formation were inhibited greatly. Based on the differential pulse voltammetry and dehydrogenase activity tests, it was verified that extracellular electron transfer was enhanced in the attached biofilms of Fe/CAC, hence improving the microbial metabolic activity and biological removal of organic matter especially DBPs precursors. Meanwhile, the extracellular polymeric substances (EPS) on the surface of Fe/CAC exhibited stronger viscosity, higher flocculating efficiency and better mechanical stability, avoiding bacteria or small-scale biofilms falling off into the water. Consequently, the microbial biomass and EPS substances amount decreased markedly in the effluent of Fe/CAC filter. More importantly, Fe/CAC did significantly enhance the shaping role on microbial community of downstream DWDSs, continuously excluding OPs advantage and inhibiting EPS production. The weakening of EPS in DWDSs resulted in decrease of microbial chlorine-resistance ability and EPS-derived DBPs precursors supply. Therefore, the deterioration of water quality in DWDSs was inhibited greatly, sustainably maintaining the safety of tap water. Our findings indicated that optimizing biological activated carbon treatment by interface modification is a promising method for improving water quality in DWDSs.