Interactive toxic effects of heavy metals and humic acids on Vibrio fischeri

Can acclimation of freshwater rotifers to silver nanoparticles or 5-fluorouracil influence their multi- and transgenerational effects?

Emerging chemical contaminants (ECCs) are among the major environmental threats in present century. A variety of ECCs is released into aquatic environments with little knowledge about their long-term impacts to organisms. We examined the role of acclimation of the freshwater rotifer Brachionus calyciflorus to silver nanoparticles (Ag-NPs) and 5-fluorouracil (5-FU) for determining their ability to deal with these ECCs individually and in mixtures along multiple generations. Additionally, transgenerational effects were also assessed during the recovery phase. Rotifers acclimated at EC10 of Ag-NPs along generations showed a higher ability to deal with higher concentrations of these nanoparticles or 5-FU along generations. Rotifers acclimated to EC10 of 5-FU showed varied responses, as their population growth rates were affected at the initial generations once exposed to higher concentration (EC50) of the same or a new contaminant; however, the rotifers acquired resistance in later generations. The exposure of generational Ag-NP-acclimated rotifers to the mixture of Ag-NPs and 5-FU at EC50 led to a shift from no effects to negative effects along successive generations, suggesting a decrease in resistance, which remained even in the post-exposure recovery phase. Similar transgenerational adverse effects were also observed for the generational Ag-NP-acclimated rotifers released from 5-FU. Rotifers acclimated to 5-FU showed a decrease in population growth rate at the first generation of recovery phase, possibly shifting their optimal environmental conditions when released from contaminants. Overall, our results suggest that rotifers had a high level of plasticity to ECC exposure in freshwaters; however, acclimation can be generic or contaminant dependent.

Acute Toxicity of Commercial Wildfire Retardants to Two Daphniid Species (Ceriodaphnia dubia and Daphnia magna)

In the face of global climate change, there has been an increase in wildfires around the world, highlighting the need for improved firefighting techniques, such as the use of fire retardants (FRs). These products can enter aquatic systems directly or through runoff, posing potential risks to aquatic biota. In this study, the acute toxicity (24-h/48-h EC50) of three distinct FRs (N-Borate, N-Phosphate+, and N-Phosphate-) was assessed on the immobility of freshwater microcrustaceans Ceriodaphnia dubia and Daphnia magna. The toxicity of the FRs varied up to two orders of magnitude, all of which presented risks to cladocerans even at dilutions much below those recommended by their manufacturers. Among the tested FRs, N-Phosphate- emerged as the most harmful to both species. Specifically, for C. dubia, the 24 h EC50 was 0.005% and the 48 h EC50 was 0.0019%, while for D. magna, 24 h EC50 was 0.003% and the 48 h EC50 was 0.0023%. With the increasing use of FRs for wildfire control, our study highlights the toxicity of newly formulated FRs to daphniid species and emphasizes the need for further evidence-based evaluations of their effects on freshwater ecosystems, which is crucial for choosing FRs that pose the lowest hazard to zooplankton communities.

A Light Touch: Solar Photocatalysis Detoxifies Oil Sands Process-Affected Waters Prior to Significant Treatment of Naphthenic Acids

Environmental reclamation of Canada's oil sands tailings ponds is among the single largest water treatment challenges globally. The toxicity of oil sands process-affected water (OSPW) has been associated with its dissolved organics, a complex mixture of naphthenic acid fraction components (NAFCs). Here, we evaluated solar treatment with buoyant photocatalysts (BPCs) as a passive advanced oxidation process (P-AOP) for OSPW remediation. Photocatalysis fully degraded naphthenic acids (NAs) and acid extractable organics (AEO) in 3 different OSPW samples. However, classical NAs and AEO, traditionally considered among the principal toxicants in OSPW, were not correlated with OSPW toxicity herein. Instead, nontarget petroleomic analysis revealed that low-polarity organosulfur compounds, composing <10% of the total AEO, apparently accounted for the majority of waters' toxicity to fish, as described by a model of tissue partitioning. These findings have implications for OSPW release, for which a less extensive but more selective treatment may be required than previously expected.

Synthetic and natural rubber associated chemicals drive functional and structural changes as well as adaptations to antibiotics in in vitro marine microbiomes

The leaching of additives from plastics and elastomers (rubbers) has raised concerns due to their potential negative impacts on the environment and the development of antibiotic resistance. In this study, we investigated the effects of chemicals extracted from two types of rubber on microbiomes derived from a benthic sea urchin and two pelagic fish species. Additionally, we examined whether bacterial communities preconditioned with rubber-associated chemicals displayed adaptations to antibiotics. At the highest tested concentrations of chemicals, we observed reduced maximum growth rates and yields, prolonged lag phases, and increased alpha diversity. While the effects on alpha and beta diversity were not always conclusive, several bacterial genera were significantly influenced by chemicals from the two rubber sources. Subsequent exposure of sea urchin microbiomes preconditioned with rubber chemicals to the antibiotic ciprofloxacin resulted in decreased maximum growth rates. This indicates a more sensitive microbiome to ciprofloxacin when preconditioned with rubber chemicals. Although no significant interaction effects between rubber chemicals and ciprofloxacin exposure were observed in bacterial alpha and beta diversity, we observed log-fold changes in two bacterial genera in response to ciprofloxacin exposure. These findings highlight the structural and functional alterations in microbiomes originating from various marine species when exposed to rubber-associated chemicals and underscore the potential risks posed to marine life.

Effect of chemical aging on phosphate adsorption and ecotoxicological properties of magnesium-modified biochar

Using magnesium-biochar composites (Mg-BC) in adsorption allows for the efficient and economically relevant removal of phosphate (PO43-) from water and wastewater. Applying Mg-BC for pollutant removal requires evaluating the adsorption capacity of composites and their ecotoxicological properties. Investigating the composite aging during the application of these composites into the soil is also essential. In the present study, nonaged and aged (at 60 or 90 °C) Mg-BC composites were investigated in the context of pyrolysis temperature (500 or 700 °C). All analyzed biochars were examined by Fourier transform infrared spectroscopy, X-ray powder diffraction, X-ray photoelectron spectroscopy, Raman spectroscopy and surface area. The content of polycyclic aromatic hydrocarbons (PAHs) (bioavailable Cfree and organic solvent-extractable Ctot), heavy metals (HMs), and environmentally persistent free radicals (EPFRs) were determined. Ecotoxicity was evaluated using tests with Folsomia candida and Allivibrio fischeri. The dependence of adsorption on pyrolysis temperature and composite aging time was observed. Changes in physicochemical properties occurring as a result of aging reduced the adsorption of PO43- on Mg-BC composites. It was found that nonaged Mg-BC700 was more effective (9.55 mg g -1) in the adsorption of PO43- than Mg-BC500 (5.75 mg g-1). The adsorption capacities of aged composites were from 21 to 61% lower than those of the nonaged composites. Due to aging, the content of Cfree PAHs increased by 3-5 times depending on the pyrolysis temperature. However, aging reduced the Ctot PAHs in all composites from 24 to 35% depending on the pyrolysis temperature. Ecotoxicological evaluation of Mg-BC composites showed increased toxicity after aging to both organisms. The use of aged BC potentially increases the contaminant content and toxicity of Mg-BC composites.

Single and mixture toxicity of cadmium and copper to swim bladder in early life stages of Japanese medaka (Oryzias latipes)

Toxicity observed in aquatic ecosystems often cannot be explained by the action of a single pollutant. Likewise, evaluation standards formulated by a single effect cannot truly reflect the environmental quality requirements. The study of mixtures is needed to provide environmental relevance and knowledge of combined toxicity. In this study, the embryos of Japanese medaka (Oryzias latipes) were treated with individual and binary mixture of copper (Cu) and cadmium (Cd) until 12 days post-fertilization (dpf). Hatching, mortality, development, histology and gene expression were assessed. Our results showed that the highest concentration mixture of Cd (10 mg/L) and Cu (1 mg/L) affected survival, hatching time and hatching success. Occurrence of uninflated swim bladder was the highest (value) with exposure to 10 mg/L Cd. Swim bladder was commonly over-inflated in a mixture (0.1 mg/L Cd + 1.0 mg/L Cu) exposure. Individuals exposed to the mixture (0.1 Cd + 1.0 Cu mg/L) showed up to a 7.69% increase in swim bladder area compared to the control group. The mixtures containing 0.1 or 10 mg/L Cd, each with 1.0 mg/L Cu resulted in significantly increased of Pbx1b expression, higher than any Cd or Cu alone (p < 0.01). In the co-exposure group (0.1/10 Cd + 1.0 Cu mg/L), Pbx1b expression was found at 12 dpf but not 7 dpf in controls. Higher concentrations of Cd may progressively reduce Pbx1b expression, potentially explaining why 75% of individuals in the 10 mg/L Cd group failed to inflate their swim bladders. Additionally, the swim bladder proved to be a valuable bio-indicator for biological evaluation.

Application of the Aliivibrio fischeri bacterium bioassay for assessing single and mixture effects of antibiotics and copper

The Aliivibrio fischeri bioassay was successfully applied in order to evaluate the acute effect of sulfamethoxazole (SMX), ciprofloxacin (CIP), chlortetracycline (CTC) and copper (Cu), alone or in binary, ternary, and overall mixture. The toxicity results are reported in terms of both effective concentrations, which inhibited 50% of the bacterium bioluminescence (EC50%), and in Toxic Units (TUs). The TUs were compared with predicted values obtained using the Concentration Addition model (CA). Finally, the toxicity of water extracts from a soil contaminated by the three antibiotics (7 mg Kg-1 each) in the presence/absence of copper (30 mg Kg-1) was also evaluated. Copper was the most toxic chemical (EC50: 0.78 mg L-1), followed by CTC (EC50: 3.64 mg L-1), CIP (96 mg L-1) and SMX (196 mg L-1). Comparing the TU and CA values of the mixtures, additive effects were generally found. However, a synergic action was recorded in the case of the CIP+Cu co-presence and antagonistic effects in the case of CTC+Cu and the ternary mixture (containing each antibiotic at 0.7 mg L-1), were identified. Soil water extracts did not show any toxicity, demonstrating the buffering ability of the soil to immobilize these chemicals.

Impact of global change on environmental hazards of different clays: A case study on Aliivibrio fischeri

The effects of global change in marine ecosystems are expected to lower pH from the current 8.1-7.5-7.0, which will have significant impacts on marine species. The purpose of this study is to investigate whether the ecotoxicity of ten different natural clays change significantly in response to the acidification process and what factors are associated with the observed changes. In this study, the ecotoxicological response of a bacterium (Aliivibrio fischeri) was tested under current (pH= 8.1) and acidified (pH 7.5 and 7.0) conditions. The ecotoxicity detected in the solid phase test (SPT protocol) and in the contact water was affected by the pH, which increased the ecotoxicity from 2/10 clays (pH 8.10) to 7/10 clays (pH 7.00), also shifting the detected effects from low to high toxicity values. The analyses performed on the natural clays studied show that pH can affect the release of metals, metalloids and rare earths from the clays into the contact water phase, affecting the toxicity observed. This phenomenon depends on the type of clay and is closely related to its mineralogical composition. As consequence, in a globally changing scenario, ecotoxicity, even of natural materials such as clay, cannot be considered stable, but must be accurately revaluated depending on the mineralogical and chemical composition of the clay. Moreover, the mineralogical composition of clays showed different efficiency in absorbing bacteria on the surface of clay particles. It was found that live bacterial cells were absorbed on the clay surface in numbers that were dependent on both clay types and pH levels.

Do new cement-based mortars pose a significant threat to the aquatic environment?

Nowadays, the use of multi-functional mortars has increased significantly, with interesting applications in the sustainable construction. In the environment, the cement-based materials are subjected to leaching, so the assessment of potential adverse effects upon aquatic ecosystem is necessary. This study focuses on the evaluation of the ecotoxicological threat and of a new type of cement-based mortar (CPM-D) and its raw materials leachates. A screening risk assessment were performed by Hazard Quotient methods. The ecotoxicological effects were investigated by a test battery with bacteria, crustacean, and algae. Two different procedures, Toxicity test Battery Index (TBI) and Toxicity Classification System (TCS), to obtain a single value for toxicity rank were used. Raw materials showed the highest metal mobility and in particular, for Cu, Cd and V potential hazard was evidenced. Leachate toxicity assessment evidenced the highest effects linked to cement and glass while the mortar showed the lowest ecotoxicological risk. TBI procedure allows a finer classification of effect linked to materials with respect to TCS which is based on worst case approach. A safe by design approach taking into account the potential and the effective hazard of the raw materials and of their combinations could allow to achieve sustainable formulations for building materials.

Can microplastics from personal care products affect stream microbial decomposers in the presence of silver nanoparticles?

Microplastics (MPs) are emerging contaminants of great concern due to their abundance and persistence over time in aquatic environments. However, studies on their impacts on freshwater organisms are scarce. In resemblance, silver nanoparticles (Ag-NPs) are incorporated into textiles and personal care products and are also classified as emerging contaminants. We used the leaf litter decomposition model system to investigate the effects of MPs from a commercially used personal care product, alone or in mixture with Ag-NPs, on the diversity and activities of freshwater microbial decomposers. We exposed stream microbial communities associated with leaf litter to increasing concentrations of MPs (polyethylene extracted from a personal care product; 100 μg L^-1 up to 1 g L^-1 5 concentrations plus 1 control) for 27 days in the absence or presence of Ag-NPs (0.1 mg L^-1 and 1 mg L^-1). The exposure to MPs, alone or in mixture with Ag-NPs, negatively affected fungal diversity and sporulation, with a reduction in leaf litter decomposition (Cohen's d > 1.5; r> 0.8; Bonferroni, P < 0.01). Shifts in community structure of sporulating fungi were observed, and effects were more pronounced in mixtures with Ag-NPs at the highest concentration. Mixtures of MPs with Ag-NPs (at the higher concentration) had the strongest impacts on extracellular enzymatic (β-glucosidase, Cohen's d > 1; r > 0.5; phenol oxidase, Cohen's d > 1; r > 0.4) activities (ANOVAs, P < 0.05). Apart from sporulation rates, observed toxicity in mixtures was lower than that expected based on individual toxicity effects, mainly for higher concentrations (Bonferroni, P < 0.05). Our study provided evidence of the potential harmful effects of MPs, alone or in mixtures with Ag-NPs, on the activities of aquatic fungi and on a key ecosystem process, determinant to organic matter turnover in streams.

Assessment of stormwater discharge contamination and toxicity for a cold-climate urban landscape

BACKGROUND

Stormwater is water resulting from precipitation events and snowmelt running off the urban landscape, collecting in storm sewers, and typically being released into receiving water bodies through outfalls with minimal to no treatment. Despite a growing body of evidence observing its deleterious pollution impacts, stormwater management and treatment in cold climates remains limited, partly due to a lack of quality and loading data and modeling parameters. This study examines the quality of stormwater discharging during the summer season in a cold-climate, semi-arid Canadian city (Saskatoon, Saskatchewan).

RESULTS

Seven stormwater outfalls with mixed-land-use urban catchments > 100 km² were sampled for four summer (June-August 2019) storm events and analyzed for a suite of quality parameters, including total suspended solids (TSS), chemical oxygen demand (COD), dissolved organic carbon (DOC), metals, and targeted polyaromatic hydrocarbons (PAHs). In addition, assessment of stormwater toxicity was done using the two toxicity assays Raphidocelis subcapitata (algae) and Vibrio fischeri (bacteria). Notable single-event, single-outfall contaminant pulses included of arsenic (420 µg/L), cadmium (16.4 µg/L), zinc (924 µg/L), fluorene (4.95 µg/L), benzo[a]pyrene (0.949 µg/L), pyrene (0.934 µg/L), phenanthrene (1.39 µg/L), and anthracene (1.40 µg/L). The IC₅₀ in both R. subcapitata and V. fischeri was observed, if at all, above expected toxicity thresholds for individual contaminant species. Principal component analysis (PCA) showed no clear trends for individual sampling sites or sampling dates. In contrast, parameters were correlated with each other in groups including DOC, COD, TSS, and reduced algal toxicity; and total dissolved solids (TDS), sum of metals, and pH.

CONCLUSIONS

In general, stormwater characteristics were similar to those of previous studies, with a bulk of contamination carried by the first volume of runoff, influenced by a combination of rainfall depth, antecedent dry period, land use, and activity within the catchment. Roads, highways, and industrial areas contribute the bulk of estimated contaminant loadings. More intensive sampling strategies are necessary to contextualize stormwater data in the context of contaminant and runoff volume peaks.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1186/s12302-022-00619-x.

Traffic-derived contaminant loading in snow storage facilities during spring melt

Stormwater results from precipitation events and melting snow running off urban landscapes and typically being released into receiving water bodies with little to no treatment. Despite evidence of its deleterious impacts, snowmelt (SM) management and treatment are limited, partly due to a lack of quality and loading data. This study examines snowmelt quality during the spring for a cold climate, semi-arid Canadian city (Saskatoon, Saskatchewan). Four snow storage facilities receiving urban snow plowed from roads in mixed land use urban catchments (228 km²) were sampled including snow piles (five events) and SM (twelve events) runoff in 2019 and 2020. Samples were analyzed for pH, EC, TDS, TSS, COD, DOC, metals, chloride, PAHs, and Raphidocelis subcapitata and Vibrio fischeri toxicity. Notable event-specific TSS spikes occurred on April 13, 2019 (3,513 mg/L), and April 24, 2019 (3,838 mg/L), and TDS, chloride, and manganese on March 26, 2020 (15,000 mg/L, 5,800 mg/L, 574 mg/L), April 17, 2020 (5,200 mg/L, 2,600 mg/L, 882 mg/L), and April 23, 2020 (5,110 mg/L, 2,900 mg/L, 919 mg/L), though chloride remained elevated through May 1, 2020, samples (1,000 mg/L). Additionally, at two sites sampled April 13, 2019, pulses of aluminum (401 mg/L) and PAHs (pyrene, phenanthrene, anthracene; 71 µg/L, 317 µg/L, 182 µg/L) were detected. Concentrations of fluorene, benzo[a]pyrene, pyrene, phenanthrene, and anthracene in almost all SP samples exceeded national aquatic toxicity guideline thresholds, while 50% of SM samples exceeded guideline thresholds for benzo[a]pyrene and pyrene, and almost all exceeded the threshold for anthracene. Nevertheless, the EC₅₀ for R. subcapitata and V. fischeri was observed, if at all, above expected toxicity thresholds.

Interaction of the Fungal Metabolite Harzianic Acid with Rare-Earth Cations (La3+, Nd3+, Sm3+, Gd3+)

Rare-earth elements are emerging contaminants of soil and water bodies which destiny in the environment and effects on organisms is modulated by their interactions with natural ligands produced by bacteria, fungi and plants. Within this framework, coordination by harzianic acid (H₂L), a Trichoderma secondary metabolite, of a selection of tripositive rare-earth cations Ln³⁺ (Ln³⁺ = La³⁺, Nd³⁺, Sm^3+, and Gd³⁺) was investigated at 25 °C, and in a CH₃OH/0.1 M NaClO₄ (50/50 w/w) solvent, using mass spectrometry, circular dichroism, UV-Vis spectrophotometry, and pH measurements. Experimental data can be satisfactorily explained by assuming, for all investigated cations, the formation of a mono-complex (LnL⁺) and a bis-complex (LnL₂^-). Differences were found between the formation constants of complexes of different Ln³⁺ cations, which can be correlated with ionic radius. Since gadolinium is the element that raises the most concern among lanthanide elements, its effects on organisms at different levels of biological organization were explored, in the presence and absence of harzianic acid. Results of ecotoxicological tests suggest that harzianic acid can decrease gadolinium biotoxicity, presumably because of complex formation with Gd³⁺.

Toxicological assessment of nanocrystalline metal alloys with potential applications in the aeronautical field

The development of new candidate alloys with outstanding characteristics for their use in the aeronautical field is one of the main priorities for the sector. In this context, nanocrystaline (nc) alloys are considered relevant materials due to their special features, such as their exceptional physical and mechanical properties. However, another important point that needs to be considered with newly developed alloys is the potential toxicological impact that these materials may have in humans and other living organisms. The aim of this work was to perform a preliminary toxicological evaluation of three nc metal alloys (WCu, WAl and TiAl) in powder form produced by mechanical alloying, applying different in vitro assays, including a mix of W-Cu powders with standard grain size in the experiments to stablish comparisons. The effects of the direct exposure to powder suspensions and/or to their derived leachates were analysed in three model organisms representative of human and environmental exposures (the adenocarcinomic human alveolar basal epithelial cell line A549, the yeast Saccharomyces cerevisiae and the Gram negative bacterium Vibrio fischeri). Altogether, the results obtained provide new insights about the potential harmful effects of the selected nc alloys, showing that, from a toxicological perspective, nc TiAl is the safest candidate in the model organisms and conditions tested.

Individual and mixed effects of anticancer drugs on freshwater rotifers: A multigenerational approach

Human population growth has led to an increased release of chemical contaminants into aquatic environments. Emerging chemical contaminants (ECCs) are of increasing concern because they can affect non-target organisms in aquatic ecosystems. The application of anticancer drugs is increasing because of enhanced cancer rates and use of chemotherapy. We assessed the impacts of two widely used anticancer drugs known for their distinct modes of action, namely 5-fluorouracil (5-FU) and doxorubicin (DOX), on the freshwater rotifer Brachionus calyciflorus across generations. Rotifer mortality (24 h) and population growth (48 h) were assessed to determine initial lethal and sub-lethal effects. Exposure of rotifers to 5-FU (up to 200 mg L^-1) did not cause mortality, while DOX caused mortality at high concentrations (EC₅₀ = 15.6 mg L^-1). Effects of 5-FU on population growth rate was higher than DOX (5-FU EC₅₀ =10.49 µg L^-1, DOX EC₅₀ = 8.78 mg L^-1). The effects of the drugs in binary mixture on population growth rates were dose dependent; significant antagonistic effects were found when 5-FU was present in the mixture at high concentrations. Finally, a transgenerational assay for five generations revealed that rotifers were able to recover their population growth rate after fourth generation when exposed to 5-FU; however, population became non-viable after the second generation of exposure to DOX. At the cellular level, accumulation of reactive oxygen species and plasma membrane damage were observed at EC₁₀ and increased at EC₅₀ for both drugs. After exposure of rotifers to 5-FU across generations, there were signs of oxidative stress recovery, as shown by a decrease in ROS accumulation and plasma membrane damage. Our results showed for the first time that the adverse effects of anticancer drugs on freshwater rotifer populations are drug and dose dependent and can persist or be attenuated along generations.

In vivo assessment of molybdenum and cadmium co-induce nephrotoxicity via NLRP3/Caspase-1-mediated pyroptosis in ducks

Excessive molybdenum (Mo) and cadmium (Cd) cause toxic effects on animals, but their joint effects on pyroptosis in kidney of ducks remain unclear. 160 healthy 7-day-old ducks were randomly divided into four groups which were fed with basal diet containing different dosages of Mo or/and Cd for 16 weeks. On the 4th, 8th, 12th and 16th weeks, kidney tissue and serum were collected. The results showed that Mo or/and Cd could significantly elevate their contents in kidney, disturb the homeostasis of trace elements, cause renal function impairment and histological abnormality, and oxidative stress as accompanied by increasing hydrogen peroxide (H₂O₂) and malondialdehyde (MDA) concentrations and decreasing glutathione peroxidase (GSH-Px), catalase (CAT) and total-superoxide dismutase (T-SOD) activities. Simultaneously, Mo or/and Cd could markedly increase interleukin-1β (IL-1β), interleukin-18 (IL-18) contents and the expression levels of pyroptosis-related genes (NOD-like receptor protein-3 (NLRP3), Caspase-1, apoptosis-associated speck-like protein (ASC), NIMA-related kinase 7 (NEK7), Gasdermin A (GSDMA), Gasdermin E (GSDME), IL-1β and IL-18) and proteins (NLRP3, Caspase-1 p20, ASC and Gasdermin D (GSDMD)). Moreover, the changes of above these indicators were more obvious in combined group. Taken together, the results illustrate that Mo and Cd might synergistically lead to oxidative stress and induce pyroptosis via NLRP3/Caspase-1 pathway, whose mechanism is somehow related to Mo and Cd accumulation in duck kidneys.

Effects of humic acid on sludge performance, antibiotics resistance genes propagation and functional genes expression during Cu(II)-containing wastewater treatment via metagenomics analysis

The humic acid (HA) function on the sludge performance, antibiotics resistance genes (ARGs) propagation and functional genes expression during Cu(II)-containing wastewater treatment was comprehensively investigated via metagenomics analysis. Results showed that the pollutants removal was significantly inhibited after long-term exposure of 5 mg/L Cu(II), while the inhibitory effects were moderately alleviated after addition of 10 mg/L HA. The extracellular polymeric substances (EPS) production with Cu(II) acclimation was higher than the sludge with Cu(II) and HA acclimation. The microbial community was significantly affected by the HA addition, while the relative abundance of dominant ARGs had no distinct differences with or without HA addition under Cu(II) stress. The functional genes were largely implemented for microbial metabolism, while no significant differences were found with HA addition under Cu(II) stress. Thus, the HA function for ARGs propagation and functional genes expression needed to be further research under Cu(II) stress in wastewater treatment.

Effect of humic acids on the toxicity of pollutants to Chlamydomonas reinhardtii: Investigation by a microscale algal growth inhibition test

Dissolved humic substances (DHSs) are the major components of organic matter in the aquatic environment. DHSs are well known to considerably affect the speciation, solubility, and toxicity of a wide variety of pollutants in the aquatic environment. In this study, the effects of the toxicity of heavy metals and hydrophobic organic pollutants (HOPs) on Chlamydomonas reinhardtii in the presence of humic acid (HA) were examined by a microscale algal growth inhibition (μ-AGI) test based on spectrophotometric detection. To clarify the relationship between the chemical properties of HAs and the toxicity change of pollutants, eight HAs from different sources were prepared and used. HAs were responsible for mitigating the toxicity of Hg, Cu, pesticides (γ-HCH, 2,4-D, and DDT), and polycyclic aromatic hydrocarbons (PAHs) such as naphthalene (Nap), anthracene (Ant), and benzo[a]pyrene (BaP). In particular, an approximately 100-fold decrease in the toxicity of BaP was observed in the presence of 10 ppm HAs extracted from tropical peat. The results indicated that the carboxylic group content and the HA molecular weight are correlated to the changes in the heavy metal toxicity. For HOPs, the aromaticity and polarity of HAs are crucial for mitigating their toxicity. Furthermore, it was clearly shown that the lake water including a high concentration of DHSs collected from Central Kalimantan, Indonesia, reduced the toxicity of Hg and γ-HCH on Chlamydomonas reinhardtii. Graphical abstract.

Selenium Prevents Lead-Induced Necroptosis by Restoring Antioxidant Functions and Blocking MAPK/NF-κB Pathway in Chicken Lymphocytes

Recent studies have identified a new existence of a genetically programmed and regulated cell death characterized by necrotic cell death morphology, termed necroptosis. Lead (Pb) is a ubiquitously distributed environmental pollutant that is highly toxic to animals and human beings. However, no detailed report has been conducted on the necroptosis in lymphocytes caused by Pb. Selenium (Se), a trace element in the body, has been shown to exert cytoprotective effect in numerous pathological injury caused by heavy metals. Here, lymphocytes isolated from chicken spleen were divided into four groups, control group, Se group, Pb group, and Pb + Se co-treatment group to investigate the potential mechanism in the necroptosis triggered by Pb and in the antagonistic effect of Se on Pb toxicity. Flow cytometry analysis and AO/EB staining showed Pb caused typical necrosis characteristics in the lymphocytes. The expression of RIP1, RIP3, and MLKL was increased, whereas the level of caspase 8 was declined in Pb group, which proved the occurrence of necroptosis. Meanwhile, Pb exposure disrupted the antioxidant enzyme (SOD, GSH-Px, and CAT) balance, promoted the expression of MAPK/NF-κB pathway factors (ERK, JNK, p38, NF-κB, and TNF-α), and activated HSPs (HSP27, HSP40, HSP60, HSP70, and HSP90). However, those Pb-induced changes were significantly alleviated in Se + Pb group. Our study revealed that Pb could trigger lymphocyte necroptosis through MAPK/NF-κB pathway activated by oxidative stress and that Se could antagonize Pb-induced necroptosis in chicken lymphocytes.

Development of Green and Sustainable Cellulose Acetate/Graphene Oxide Nanocomposite Films as Efficient Adsorbents for Wastewater Treatment

: Novel ecofriendly adsorbents, cellulose acetate/graphene oxide (CA-GO) nanocomposite, were prepared from sugarcane bagasse agro-waste for removing Ni²⁺ ions from wastewater. Graphene oxide (GO) was prepared by the oxidation of sugarcane bagasse using ferrocene under air atmosphere. Cellulose acetate (CA) was also prepared from sugarcane bagasse by extraction of cellulose through a successive treatments with sulfuric acid (10% v/v), sodium hydroxide (5% w/v), ethylenediaminetetraacetic acid, and hydrogen peroxide, and finally , followed by acetylation. CA-GO was prepared via mixing of GO and CA in the presence of calcium carbonate and different concentrations of GO, including 5, 10, 15, 20, 25, and 30 wt% relative to the weight of CA. The CA-GO nanocomposite showed porous microstructures with high surface area, which enhance their ability towars the adsorption of Ni²⁺ ions from wastewater. The morphological properties of the prepared adsorbents were explored by scanning electron microscope (SEM) and Fourier-transform infrared spectroscopy (FT-IR). The efficiency of the CA-GO towards the adsorption of Ni²⁺ ions from wastewater was explored against as time, temperature, and total content of Ni²⁺ ions. The adsorption measurements of Ni²⁺ ions were investigated within the concentration range of 10-40 mg/L, time range between 15 and 90 minutes, and temperature range between 25 °C and 55 °C. The results displayed a considerable improvement in the adsorption process of Ni²⁺ ions by CA-GO-2 with a removal efficiency of 96.77%. The isotherms were monitored to best fit the Langmuir model. Finally, the adsorption performance of the prepared CA-GO nanocomposite films demonstrated promising properties as green, sustainable and cheap adsorbents for water pollutants.

Addressing the electrostatic component of protons binding to aquatic nanoparticles beyond the Non-Ideal Competitive Adsorption (NICA)-Donnan level: Theory and application to analysis of proton titration data for humic matter

HYPOTHESIS

Charge descriptors of aquatic nanoparticles (NPs) are evaluated from proton titration curves measured at different salt concentrations and routinely analysed by the Non-Ideal Competitive Adsorption-Donnan (NICAD) model. This model, however, suffers from approximations regarding particle electrostatics, which may bias particle charge estimation. Implementation of Poisson-Boltzmann (PB) theory within consistent treatment of NPs protolytic data is expected to address NICAD shortcomings.

EXPERIMENTS

An alternative to NICAD is elaborated on the basis of nonlinearized PB equation for soft particle electrostatics to properly unravel the electrostatic and chemical components of proton binding to NPs. A numerical package is developed for automated analysis of proton titration curves and proton affinity spectra at different salt concentrations. The performance of the method is illustrated for humic matter nanoparticles with different charge and size, and compared to that of NICAD.

FINDINGS

Unlike NICAD, PB-based treatment successfully reproduces particle charge dependence on pH for practical salt concentrations from the thin to thick electric double layer limit. Donnan representation in NICAD leads to moderate to dramatic misestimations of proton affinity and binding heterogeneity depending on particle size to Debye layer thickness ratio. Interpretation of NPs protolytic properties with PB theory further avoids adjustment of the 'particle Donnan volume' empirically introduced in NICAD.

Long-term exposure to copper induces autophagy and apoptosis through oxidative stress in rat kidneys

Copper (Cu) is an essential trace element for most organisms. However, excessive Cu can be highly toxic. The purpose of this study was to elucidate the mechanism underlying Cu toxicity in the kidneys of rats after treatment with CuCl₂ (15 [control], 30, 60, or 120 mg/kg in the diet) for 180 days. Histological and ultrastructural changes, antioxidant enzyme activity, and the mRNA and protein levels of apoptosis and autophagy-related genes were measured. The results showed that Cu exposure led to significant accumulation of copper in kidneys and disorganized kidney morphology. The activities of total anti-oxidation capacity (T-AOC) and superoxide dismutase (SOD) in the kidneys decreased significantly, while the malondialdehyde (MDA) content increased. Furthermore, excessive Cu markedly upregulated the expression of autophagy and apoptosis-related genes (LC3A, LC3B, ATG-5, Beclin-1, Caspase3, CytC, P53, Bax), but downregulated the expression of P62, mTOR and BCL-2. Moreover, the LC3B/LC3A, ATG-5, Beclin-1, P53, Caspase3 proteins were up-regulated while P62 was down-regulated in the kidney tissues of the treatment groups. Overall, these findings provide strong evidence that excess Cu can trigger autophagy and apoptosis via the mitochondrial pathway by inducing oxidative stress in rat kidneys.

Radiometrical and physico-chemical characterisation of contaminated glass waste from a glass dump in Sweden

Around former glass factories in south eastern Sweden, there are dozens of dumps whose radioactivity and physico-chemical properties were not investigated previously. Thus, radiometric and physico-chemical characteristics of waste at Madesjö glass dump were studied to evaluate pre-recycling storage requirements and potential radiological and environmental risks. The material was sieved, hand-sorted, leached and scanned with X-Ray Fluorescence (XRF). External dose rates and activity concentrations of Naturally Occurring Radioactive Materials from ²³⁸U, ²³²Th series and ⁴⁰K were also measured coupled with a radiological risk assessment. Results showed that the waste was 95% glass and dominated by fine fractions (<11.3 mm) at 43.6%. The fine fraction had pH 7.8, 2.6% moisture content, 123 mg kg^-1 Total Dissolved Solids, 37.2 mg kg^-1 Dissolved Organic Carbon and 10.5 mg kg^-1 fluorides. Compared with Swedish EPA guidelines, the elements As, Cd, Pb and Zn were in hazardous concentrations while Pb leached more than the limits for inert and non-hazardous wastes. With ⁴⁰K activity concentration up to 3000 Bq kg^-1, enhanced external dose rates of ⁴⁰K were established (0.20 μSv h^-1) although no radiological risk was found since both External Hazard Index (H_ex) and Gamma Index (I_γ) were <1. The glass dump needs remediation and storage of the waste materials under a safe hazardous waste class 'Bank Account' storage cell as a secondary resource for potential future recycling.

The mixture toxicity of heavy metals on Photobacterium phosphoreum and its modeling by ion characteristics-based QSAR

Organisms are frequently exposed to mixtures of heavy metals because of their persistence in the environment. The mixture toxicity of heavy metals should therefore be evaluated to perform a rational environmental risk assessment for organisms. In this study, we determined the inhibition toxicity of five heavy metals (Cu²⁺, Co²⁺, Zn²⁺, Fe³⁺ and Cr³⁺) and their binary mixtures to Photobacterium phosphoreum (P. phosphoreum). We obtained the following results: (1) the order of individual toxicity was Zn²⁺>Cu²⁺>Co²⁺>Cr³⁺>Fe³⁺, and (2) different combined effects (additive, synergistic and antagonistic) were observed in the binary mixtures of heavy metals, with toxicity unit (TU) values ranging from 0.15 to 3.50. To predict the mixture toxicity of heavy metals, we derived the ion characteristic parameters of heavy metal mixtures and explored the ion-characteristic-based quantitative structure–activity relationship (QSAR) model (R² = 0.750, Q² = 0.649). The developed QSAR model indicated that the mixture toxicity of heavy metals is related to the change in ionization potential ((ΔIP)^mix), the first hydrolysis constant (log(KOH)^mix) and the formation constant value (logKfmix).

Ecotoxicity of pore water in soils developed on historical arsenic mine dumps: The effects of forest litter

Arsenic release from dump soils in historical mining sites poses the environmental risk. Decomposing forest litter can affect mobilization of As and other toxic elements, change their speciation in pore water and influence the toxicity to biota. This study examined the chemistry and ecotoxicity of pore water acquired from four soils that developed on the dumps in former As mining sites, in the presence and absence of forest litter collected from beech and spruce stands. Soils contained 1540-19600 mg/kg of As. Pore water was collected after 2, 7, 21 and 90 days of incubation, using MacroRhizon suction samplers. Its chemical analysis involved determination of pH, the concentrations of As, Cu and Pb (the elements with high enrichment factor Igeo>3), as well as metals considered most mobile: Cd, Zn and Mn. Ecotoxicity of pore water was examined in three bioassays: Microtox, MARA and Phytotox with Sinapis alba as test plant. The release of As, unlike heavy metals, was particularly intensive from the soils with neutral and alkaline pH. The concentrations of toxic elements in pore water were in broad ranges, up to dozens mg/L. The results of Phytotox had a poor precision, but their means correlated well with As concentrations in pore water, which indicates that As made a crucial factor of phytotoxicity. The outcomes of Microtox bioassay indicated poorer relationships between As concentrations and toxicity, and other factors contributed to ecotoxicity at very low and very high As concentrations. The highest toxicity was recorded from the soils treated with forest litter. MARA turned out to be not sensitive enough to give reproducible results in experimental conditions. The PCA analysis confirmed that the growth of microbes in MARA bioassay was poorly dependent on As and metals in pore water except for a yeast Pichia anomala (No 11). The results let us conclude that the bioassays Phytotox and Microtox can provide useful information on ecotoxicity of pore water in soils that develop on As-rich dumps whereas applicability of MARA in those conditions proved limited.

Avian Stress-Related Transcriptome and Selenotranscriptome: Role during Exposure to Heavy Metals and Heat Stress

Selenium, through incorporation into selenoproteins, is one of the key elements of the antioxidant system. Over the past few years there has been increased interest in exploring those molecular mechanisms in chicken, responsible for the development of this protection system. In more detail, Cd/Pb poisoning and heat stress increase oxidation, mRNA levels of inflammatory proteins, and apoptotic proteins. Selenium seems to enhance the antioxidant status and alleviates these effects via upregulation of antioxidant proteins and other molecular effects. In this review, we analyze avian transcriptome key elements with particular emphasis on interactions with heavy metals and on relation to heat stress.

The antagonistic effect of Se on the Pb-weakening formation of neutrophil extracellular traps in chicken neutrophils

Neutrophils represent an important part of the body's innate immunity and can resist the invasion of pathogenic microorganisms by releasing neutrophil extracellular traps (NETs). In this study, we investigated the toxic effects of lead (Pb) on the release of NETs, the antagonism of selenium (Se) on Pb toxicity and the potential molecular mechanisms. Our model was an in vitro exposure model for the addition of Se, Pb or both in the culture medium and was based on the separation of neutrophils from the peripheral blood of healthy chickens. Phorbol-myristate-acetate (PMA) was used as a stimulant. The scanning electron microscopy and fluorescence microscopy results showed that Pb weakened the PMA-induced formation of NETs. Exposure to Pb reduced the expression of the extracellular regulated protein kinase (ERK) pathway and the respiratory burst. Exposure to Pb also attenuated the release of Ca²⁺ in the endoplasmic reticulum mediated by the inositol 1,4,5-trisphosphate receptor (IP3R). These are two ways by which Pb decreases the formation of NETs. Pb also attenuates the expression levels of myeloperoxidase (MPO) and neutrophil elastase (NE), and attenuates histone removal by affecting the expression of different protein kinase C (PKC) isoforms. In contrast, Se can reduce the toxic damage caused by Pb. These results indicate that exposure to Pb decreases the formation of NETs, while Se can antagonize the toxicity of Pb to allow the formation of NETs.

Influence of humic substances on the toxic effects of cadmium and SDBS to the green alga Scenedesmus obliquus

The joint toxicity of chemicals mixture in the aquatic environment was still not well clear. To clarify the joint toxicity of the mixtures of metals and organic pollutants, as well as the influence of dissolved organic matter (DOM) in field water-body on their toxic effects, we conducted the toxicity tests with cadmium (Cd) and sodium dodecyl benzene sulfonate (SDBS) on Scenedesmus obliquus (S. obliquus) with or without the presence of fulvic acid (FA), a typical of DOM. Our results showed Cd was more toxic to S. obliquus than SDBS, and the effects of fulvic acid on SDBS were greater than Cd. The joint toxicity of Cd and SDBS expressed a synergistic effect on S. obliquus, which was observed to be increased with the presence of FA. Our results gave an example for the joint toxicity investigations of organics and metals, aiding to understanding the toxicity of pollutant mixtures in field water bodies containing DOM.

Evaluation of Single and Joint Toxicity of Perfluorinated Carboxylic Acids and Copper to Metal-Resistant Arthrobacter Strains

Perfluorocarboxylic acid compounds (PFCAs) and copper have been regarded as ubiquitous environmental contaminants in aquatic ecosystems worldwide. However, data on their possible joint toxic effects on microorganisms are still lacking. To study the combined effects of four PFCAs with different carbon chain lengths and copper, a series of experiments were conducted to explore the acute toxicity of these PFCAs in the absence and presence of copper on a metal-resistant Arthrobacter strain GQ-9 by microcalorimetry. The thermokinetic parameters, including growth rate constant (k), inhibitory ratio (I), and half inhibitory concentration (IC₅₀), were calculated and compared using the data obtained from the power-time curves. Our work revealed that GQ-9 is more resistant to perfluorooctanoic acid (PFOA) than Escherichia coli. The single and joint toxicity of PFCAs with copper are dose- and carbon chain length-dependent. The longer the carbon chain length of PFCAs, the higher the toxicity. In addition, PFCAs interacted synergistically with copper. This work could provide useful information for the risk assessment of co-exposure to perfluorinated compounds and heavy metals in natural environments.

Molybdenum and Cadmium exposure influences the concentration of trace elements in the digestive organs of Shaoxing duck (Anas platyrhyncha)

To investigate the toxic effects of Molybdenum (Mo) and Cadmium (Cd) on trace elements in digestive organs of Shaoxing duck (Anas platyrhyncha), 120 Shaoxing ducks were randomly divided into control group and 5 treatment groups which were treated with a commercial diet containing different dosages of Mo and Cd. On the 60th and 120th days, the beak, esophagus, glandular stomach, muscular stomach, small intestine, large intestine and feces were collected to determine contents of Mo, Cd, copper (Cu), iron (Fe), zinc (Zn) and selenium (Se), then correlation analysis was performed. The results showed that Cd content in digestive organs significantly increased in co-treated groups compared to single treated groups and Mo concentration increased in Mo-treated groups compared to control group, whereas Cu, Fe, Zn and Se concentrations in digestive organs decreased in co-treated groups. Furthermore, Cd and Mo were mainly accumulated in the small intestine and esophagus, respectively. There was a strongly positive correlation between Cd and Mo while they had negative correlation with Cu, Fe, Zn and Se, respectively. In feces, Mo and Fe contents in high dose of Mo group and high Mo combined with Cd group were significantly higher than those in control group, and Cu content in all treated groups significantly increased and Cd, Zn and Se concentrations had no difference. The results indicated that dietary Mo or/and Cd might disturb homeostasis of trace elements in digestive organs of Shaoxing duck. Moreover, the two elements presented a synergistic relationship.

Chemical toxicity and ecotoxicity evaluation of tannery sludge stabilized with ladle furnace slag

In this study, the stabilization of tannery sludge, which produced during the physico-chemical treatment of tannery wastewaters, was examined by the addition of ladle furnace slag. Moreover, the simultaneous addition of organoclay and ladle furnace slag for the stabilization of tannery sludge was also examined. Chromium and dissolved organic carbon in the leachate of raw tannery sludge, using the EN 12457-2 standard leaching test, were found to exceed the limit values for disposal in non-hazardous and even in hazardous waste landfills, according to the EU Decision 2003/33/EC. Tannery waste (air-dried sludge) was mixed with ladle furnace slag and water or ladle furnace slag, organoclay and water at different ratios, in order to study the stabilization of chromium and organic compounds. The mixtures were left for one week aging and then they were subjected to the standard leaching test EN 12457-2. The leachate of tannery waste stabilized with ladle furnace slag showed Cr concentrations below the respective regulation limit value for disposal in non-hazardous waste landfills; however, the dissolved organic carbon cannot meet the respective limit value. On the other hand, the leachate of tannery waste stabilized with a mixture of ladle furnace slag and organoclay, using 30:50:20 mass ratio, presented both Cr and dissolved organic carbon concentrations below the regulation limit values for disposal in non-hazardous waste landfills. Moreover, this leachate was further subjected to ecotoxicity test, using the Vibrio fischeri photo-bacterium. The leachate of stabilized tannery waste showed reduced ecotoxicity, in comparison with the toxicity effect of the leachate of the untreated tannery waste.

Vibrio fischeri bioluminescence inhibition assay for ecotoxicity assessment: A review

Vibrio fischeri bioluminescence inhibition bioassay (VFBIA) has been widely applied for the monitoring of toxicity on account of multiple advantages encompassing shorter test duration, sensitive, cost-effective and ease of operation. Moreover, this bioassay found to be equally applicable to all types of matrices (organic & inorganic compounds, metals, wastewater, river water, sewage sludge, landfill leachate, herbicides, treated wastewater etc.) for toxicity monitoring. This review highlights the apparent significance of Vibrio fischeri bioluminescence inhibition assay for ecotoxicological screening and evaluation of diverse chemical substances toxicity profile. The biochemical and genetic basis of the bioluminescence assay and its regulatory mechanism have been concisely discussed. The basic test protocol with ongoing improvements, widespread applications, typical advantages and probable limitations of the assay have been overviewed. The sensitivity of VFBIA and toxicity bioassays has also been compared.

Effects of single and combined exposures to copper and benzotriazole on Eisenia fetida

Benzotriazole (BTR), an emerging class of environmental pollutant, is widely used in industrial applications and household dishwashing agents. Despite the reported toxicity of BTR to aquatic organisms, little is known about its effects on terrestrial invertebrates. Copper (Cu) accumulates in agricultural soils receiving urban waste products, fertilizers, fungicides, and urban sewage. In this study, two different types of bioassays (acute toxicity test and behavioral toxicity test) were performed to evaluate the toxicity of Cu and BTR, both singly and together, on the earthworm (Eisenia fetida) in artificial soil. The results of avoidance behaviour tests showed that the EC_50,48 h values for Cu and BTR were 1.47 and 0.46 mmol kg^-1, respectively. The results of the acute toxicity tests showed that the LC_50,7 d and LC_50,14 d of Cu in earthworms were 9.19 and 5.28 mmol kg^-1, respectively, and the LC_50,7 d and LC_50,14 d of BTR were 2.43 and 1.76 mmol kg^-1, respectively. Toxicity analysis demonstrated that the binary BTR and Cu mixture had predominantly antagonistic effects on the avoidance behaviour and survival of earthworms. The Cu²⁺ activities and mortality of earthworms decreased significantly with increasing concentrations of BTR, while the solid-liquid distribution coefficient of Cu increased. These results indicated that the presence of BTR can reduce the toxicity as well as the bioavailability of Cu in soil with both BTR and Cu.

Aquatic ecotoxicity of ashes from Brazilian savanna wildfires

In a global scenario of climate change, several studies have predicted an increase in fires in different parts of the world. With the occurrence of rains following the fires in the Brazilian savanna (Cerrado biome), the compounds present in ashes may enter aquatic environments and cause adverse effects to these ecosystems. In this context, this study evaluated the potential toxicity of ashes from two areas of Cerrado and an area of pasture, through ecotoxicological bioassays and using three aquatic species from distinct trophic levels, which were exposed to different dilutions of ashes: the microcrustacean Ceriodaphnia dubia, the fish Danio rerio and the mollusc Biomphalaria glabrata. The ashes from the three sampled areas showed higher concentrations of some elements in relation to the soil samples (B, Ca, K, Mg, Mn, P, S, Si, Sr, Zn), but only a small quantity of these compounds was solubilised. Our data showed that all ash samples caused acute toxicity to C. dubia (48hs-LC₅₀ = 13.4 g L^-1; 48hs-LC₅₀ = 6.33 g L^-1; 48hs-LC₅₀ = 9.73 g L^-1 respectively for transition area, pasture, typical cerrado areas), while in relation to D. rerio and B. glabrata, no acute toxicity was observed when they were exposed to ashes from native Cerrado vegetation and pasture areas. Ashes from a transition area showed toxicity for D. rerio (48hs-LC₅₀ = 25.0 g L^-1); possibly, this was due to the combination of multiple preponderant inorganic elements of ashes with other organic compounds not analysed, such as polycyclic aromatic hydrocarbons (PAHs). In summary, these results suggest that wildfires may pose risks to zooplankton communities and emphasize the need for more studies to better understand the complexity of the ecological effects of fire on aquatic ecosystems.

Effects of selenium-lead interaction on the gene expression of inflammatory factors and selenoproteins in chicken neutrophils

Lead (Pb) is one of the most highly toxic metal pollutant that can cause damage to the immune system. It is known that selenium (Se) can antagonize heavy metals. To explore the toxic effects of Pb poisoning on bird immune cells, as well as the alleviating effects of Se on Pb, Se supplement and/or Pb poisoning chicken models were established. One hundred and eighty Hyline 7-day-old male chickens received either Se (1mg Se per kg of diet), Pb (350mg Pb per liter water) or Se+Pb in their diet and water for 90 days. Then, whole blood was collected from the four groups of chickens, and serum and neutrophils were isolated. The levels of Se and Pb in chicken serum, mRNA levels of 24 selenoproteins (GPX1, GPX2, GPX3, GPX4, Dio1, Dio2, Dio3, Txnrd1, Txnrd2, Txnrd3, SELS, SPS2, SELK, SELW1, SEP15, SEPX1, SELT, SELI, SELO, SELM, SEPN1, SEPP1, SELU, SELH) and inflammatory factors (TNF-α, COX-2, iNOS, NF-κB), and iNOS protein level in chicken neutrophils were determined, and protein-protein interaction prediction and principal component analysis were performed. The data showed that Pb exposure increased Pb content in serum, activated the NF-κB pathway, and increased the expression of selenoproteins in chicken neutrophils. Se supplements could reduce Pb concentration in serum, had a mitigative effect on the activation of the NF-κB pathway and further enhanced the upward trend of selenoprotein expression induced by Pb exposure. These results suggest that Se supplement could eliminate Pb in serum and alleviate the activation of the NF-κB pathway under Pb exposure by increasing the expression of selenoproteins.

Potential impact of flowback water from hydraulic fracturing on agricultural soil quality: Metal/metalloid bioaccessibility, Microtox bioassay, and enzyme activities

Hydraulic fracturing has advanced the development of shale gas extraction, while inadvertent spills of flowback water may pose a risk to the surrounding environment due to its high salt content, metals/metalloids (As, Se, Fe and Sr), and organic additives. This study investigated the potential impact of flowback water on four representative soils from shale gas regions in Northeast China using synthetic flowback solutions. The compositions of the solutions were representative of flowback water arising at different stages after fracturing well establishment. The effects of solution composition of flowback water on soil ecosystem were assessed in terms of metal mobility and bioaccessibility, as well as biological endpoints using Microtox bioassay (Vibrio fischeri) and enzyme activity tests. After one-month artificial aging of the soils with various flowback solutions, the mobility and bioaccessibility of As(V) and Se(VI) decreased as the ionic strength of the flowback solutions increased. The results inferred a stronger binding affinity of As(V) and Se(VI) with the soils. Nevertheless, the soil toxicity to Vibrio fischeri only presented a moderate increase after aging, while dehydrogenase and phosphomonoesterase activities were significantly suppressed with increasing ionic strength of flowback solutions. On the contrary, polyacrylamide in the flowback solutions led to higher dehydrogenase activity. These results indicated that soil enzyme activities were sensitive to the composition of flowback solutions. A preliminary human health risk assessment related to As(V) suggested a low level of cancer risk through exposure via ingestion, while holistic assessment of environmental implications is required.

Lead and PAHs contamination of an old shooting range: A case study with a holistic approach

Soil pollution at firing ranges is an issue of growing importance, due to the accumulation in soils of contaminants derived from ammunition and clay targets. The concentration of Pb and PAHs was determined in five soils of an abandoned shooting range in Galicia (northwest Spain), and an ecotoxicological characterization was performed in order to obtain an assessment of risks. Therefore, the retention capacity of soils was assessed using test organisms of different trophic levels, and the role of soils as habitat for soil invertebrates was assessed by reproduction tests and bioaccumulation assays with earthworms. The sum of 15 PAHs ranged between 38 and 360mgkg^-1, which exceed, together with Pb (160-720mgkg^-1), the Galician generic reference value for urban and sporting field soils. Bioaccumulation in E. andrei showed contents up to 104,000μgPbkg^-1_dw, and up to 645μgPAHskg^-1_fw. High contents of Pb and PAHs in soil samples and in Eisenia andrei whole body, caused a reduction in the number of juveniles produced, whereas, Vibrio fischeri, Raphidocelis subcapitata and Daphnia magna displayed a slight toxic response to the soil elutriates tested. Therefore, the function of these soils to retain contaminants seemed not compromised, probably due to the high organic matter content and pH values, which are weakly acidic. The habitat function was affected, indicating that soil solution is not the only route of exposure to contaminants to E. andrei. The integration of chemical and ecotoxicological lines of evidence give rise to high risks values, restricting the use of these areas, and pointing for risks to surrounding ecosystems due to possible trophic transferences. The calculation of risks using the chemical and ecotoxicological data, required by Spanish legislation, could be a good approach to communicate with those responsible and/or involved in the management of contaminated sites.

Distribution, migration and potential risk of heavy metals in the Shima River catchment area, South China

The distribution, migration and potential risk of heavy metals in water and soil environments, related to city water supply, were investigated. Heavy metal concentrations in waters from the Shima River water ranged from not detected (n.d.) to 749 μg L(-1) for Mn, n.d. to 151 μg L(-1) for Ni, 7.00 to 494 μg L(-1) for Zn, n.d. to 93.0 μg L(-1) for Cu and n.d. to 9860 μg L(-1) for Fe. The highest concentration of heavy metals was found at an upstream site in February as a result of industrial effluent discharge. Groundwater (GW1-GW5) and soil (S1-S8) samples along the riverbank showed similar levels of contamination due to a close hydraulic relationship and frequent exchange of water, probably resulting in migration of heavy metals from river water to the aquifer and accumulation at the interface. The mean concentrations of heavy metals in soil profiles were in the ranges of 2.50-19.0 mg kg(-1) for As, 2.80-11.2 mg kg(-1) for Cd, 20.3-165 mg kg(-1) for Cr, 14.5-298 mg kg(-1) for Cu, 11.4-102 mg kg(-1) for Ni, 7.00-95.0 mg kg(-1) for Pb, 40.4-465 mg kg(-1) for Zn, 8.80 × 10(3)-21.8 × 10(3) mg kg(-1) for Fe, and 62.2-430 mg kg(-1) for Mn, showing severe soil pollution by Cd. LUMISTox testing and the potential ecological risk index (RI) were used to assess the potential for adverse ecological effects caused by heavy metals in water and soil media. River water samples posed slight acute toxicity to Vibrio fischeri with luminescence inhibition rates (LIRs) ranging from 24.6% to 38.4% in February. Elevated Zn and Cu concentrations significantly contributed to the toxicity. However, groundwater did not exhibit any toxicity to Vibrio fischeri. The severity of the potential ecological risk for individual metals (Er(i)) decreased in the order of Cd > Cu > Ni > As > Pb > Zn > Cr. RI values indicated that all soil samples in the study area posed a high level of ecological risk. Cd contributed significantly (95.5-98.9%) to potential ecological risk in soils.

Evaluation of interactions between soil and coal fly ash leachates using column percolation tests

The aim of this work was the assessment of the environmental impact of different origin fly ashes with regard to their final disposal. The experimental procedure included the performance of single column tests and column tests of fly ash and soil in series. The appraisal of the potential environmental hazards was implemented using physicochemical analyses and bioassays. Two different fly ash samples were examined, one fly ash produced from the combustion of sub-bituminous coal (CFA) and one fly ash produced from the combustion of lignite (LFA). Single column percolation tests were performed according to NEN 7343 protocol, while fly ash/soil experiments were conducted incorporating slight modifications to this protocol. The study focused on the release of metals Ba, Cr, Cu, Mo, Se and Zn and the ecotoxic behavior of leachates on crustacean Daphnia magna and bacteria Vibrio fischeri. The infiltration of the leachates of both fly ashes through soil affected considerably their leaching profile. The transport of Cu and Zn was facilitated by the dynamic leaching conditions and influenced by the pH of the leachates. Moreover, the release and bioavailability of Cr, Cu and Zn was probably altered during the infiltration experiments and organisms' response was not always correlated with the concentration of metals. Nevertheless, the results are signalling that possible manipulations and final disposal of fly ash should be considered when environmental threats are investigated.

Assessing and monitoring the ecotoxicity of pulp and paper wastewater for irrigating reed fields using the polyurethane foam unit method based on monitoring protozoal communities

Using the standardized polyurethane foam unit (PFU) method, a preliminary investigation was carried out on the bioaccumulation and the ecotoxic effects of the pulp and paper wastewater for irrigating reed fields. Static ectoxicity test had shown protozoal communities were very sensitive to variations in toxin time and effective concentration (EC) of the pulp and paper wastewater. Shannon-Wiener diversity index (H) was a more suitable indicator of the extent of water pollution than Gleason and Margalef diversity index (d), Simpson's diversity index (D), and Pielou's index (J). The regression equation between S eq and EC was S eq  = - 0.118EC + 18.554. The relatively safe concentration and maximum acceptable toxicant concentration (MATC) of the wastewater for the protozoal communities were about 20 % and 42 %, respectively. To safely use this wastewater for irrigation, more than 58 % of the toxins must be removed or diluted by further processing. Monitoring of the wastewater in representative irrigated reed fields showed that the regularity of the protozoal colonization process was similar to the static ectoxicity, indicating that the toxicity of the irrigating pulp and paper wastewater was not lethal to protozoal communities in the reed fields. This study demonstrated the applicability of the PFU method in monitoring the ecotoxic effects of pulp and paper wastewater on the level of microbial communities and may guide the supervision and control of pulp and paper wastewater irrigating within the reed fields ecological system (RFES).

An ecotoxicological evaluation of soil fertilized with biogas residues or mining waste

This paper presents an ecotoxicological evaluation of soil fertilized with biogas digestate (BD) or mining waste (MS). The study was performed under pot experiment conditions. BD was added at a dose of 1.5 and 3% to the soil. MS was applied at a dose of 10 and 20%. Samples were collected at the beginning of the experiment and after 180 and 360 days from the start of the study. In addition, a parallel experiment with the addition of CaO was done. This was designed to eliminate the adverse effect of low soil pH on the test organisms. A battery of ecotoxicological tests was used based on tests with plants (Phytotoxkit F), microorganisms (Microtox), and crustaceans (Daphtoxkit F). In most cases, the obtained results showed that the investigated wastes had a stimulating effect on the growth of Lepidium sativum roots. The highest content of BD was an exception since it inhibited the growth of L. sativum roots. After adding BD and MS, both the luminescence of Vibrio fischeri and the mortality of Daphnia magna was at a similar level to that in the control soil. An exception was the significant increase in the mortality of D. magna after 48 h for soil with 3% BD. The tests performed after 6 and 12 months showed that, with time, the toxicity of the waste-amended soil fluctuated, but ultimately decreased in most cases compared to the control. The effect of the addition of CaO on the examined toxicity parameters was different and depended on the experimental variant.

Acute toxicity of Hg, Cd, and Pb towards dominant bacterial strains of sequencing batch reactor (SBR)

One of the most important factors that affect the operation efficiency of sequencing batch reactor (SBR) technology is bacterial viability and biomass activity. The acute toxicity of three heavy metals to four dominant strains of sequencing batch reactor (Pseudomonas, Aeromonas, Enterobacter, and Bacillus) was investigated using a resazurin bioassay. After exposing the bacterial strains to soluble compound of Hg, Cd, and Pb, at more than five selected concentrations, the median effective concentration (EC50) and the mortality rate values were calculated. Large differences were observed in sensitivities of the four bacterial strains to the metals. Pseudomonas showed the highest sensitivity for Cd (EC₅₀ = 0.06 μmol/L) and Hg (EC₅₀ = 11.75 μmol/L), while Aeromonas showed the highest sensitivity for Pb (EC₅₀ = 48.27 μmol/L). Considering the EC50 test results, it was concluded that Pseudomonas and Aeromonas are excellent and reliable bioindicators for assessing the toxicity of water and wastewaters polluted by Cd, Hg, and Pb. The rapidity (30 min) and simplicity of the resazurin bioassay procedure enable this enzymatic test to be used in toxicity assessment of small and decentralized wastewater treatment plants (WWTPs).

Effect of dissolved humic acid on the Pb bioavailability in soil solution and its consequence on ecological risk

Current risk characterization in ecological risk assessment does not consider bioavailability of heavy metals, which highly depends on physicochemical properties of environmental media. This study was set to investigate the effect of humic acid (HA), used as a surrogate of organic matter, on Pb toxicity and the subsequent effect on risk characterization in ecological risk assessment. Pb toxicity was assessed using Microtox(®) in the presence and absence of two different forms of HA, particulate HA (pHA) and dissolved HA (dHA). With increasing contact time, the EC10 values increased (i.e., the toxic effects decreased) and the dissolved Pb concentrations of the filtrates decreased. The high correlation (R = 0.88, p < 0.001) between toxic effects determined using both the mixture and its filtrate as exposure media leads us to conclude that the Pb toxicity highly depends on the soluble fraction. Also, reduced Pb toxicity with increasing dHA concentrations, probably due to formation of Pb-dHA complexes, indicated that Pb toxicity largely comes from free Pb ions. Overall, this study shows the effect of HA on metal toxicity alleviation, and emphasizes the need for incorporating the bioavailable heavy metal concentrations in environmental media as a point of exposure in ecological risk assessment.

Microencapsulated Aliivibrio fischeri in alginate microspheres for monitoring heavy metal toxicity in environmental waters

In this article a luminescence fiber optic biosensor for the microdetection of heavy metal toxicity in waters based on the marine bacterium Aliivibrio fischeri (A. fischeri) encapsulated in alginate microspheres is described. Cu(II), Cd(II), Pb(II), Zn(II), Cr(VI), Co(II), Ni(II), Ag(I) and Fe(II) were selected as sample toxic heavy metal ions for evaluation of the performance of this toxicity microbiosensor. The loss of bioluminescence response from immobilized A. fischeri bacterial cells corresponds to changes in the toxicity levels. The inhibition of the luminescent biosensor response collected at excitation and emission wavelengths of 287 ± 2 nm and 487 ± 2 nm, respectively, was found to be reproducible and repeatable within the relative standard deviation (RSD) range of 2.4-5.7% (n = 8). The toxicity biosensor based on alginate micropsheres exhibited a lower limit of detection (LOD) for Cu(II) (6.40 μg/L), Cd(II) (1.56 μg/L), Pb(II) (47 μg/L), Ag(I) (18 μg/L) than Zn(II) (320 μg/L), Cr(VI) (1,000 μg/L), Co(II) (1700 μg/L), Ni(II) (2800 μg/L), and Fe(III) (3100 μg/L). Such LOD values are lower when compared with other previous reported whole cell toxicity biosensors using agar gel, agarose gel and cellulose membrane biomatrices used for the immobilization of bacterial cells. The A. fischeri bacteria microencapsulated in alginate biopolymer could maintain their metabolic activity for a prolonged period of up to six weeks without any noticeable changes in the bioluminescence response. The bioluminescent biosensor could also be used for the determination of antagonistic toxicity levels for toxicant mixtures. A comparison of the results obtained by atomic absorption spectroscopy (AAS) and using the proposed luminescent A. fischeri-based biosensor suggests that the optical toxicity biosensor can be used for quantitative microdetermination of heavy metal toxicity in environmental water samples.

Amendment application in a multi-contaminated mine soil: effects on soil enzymatic activities and ecotoxicological characteristics

Several amendments were tested on soils obtained from an arsenopyrite mine, further planted with Arrhenatherum elatius and Festuca curvifolia, in order to assess their ability to improve soil's ecotoxicological characteristics. The properties used to assess the effects were: soil enzymatic activities (dehydrogenase, β-glucosidase, acid phosphatase, urease, protease and cellulase), terrestrial bioassays (Eisenia fetida mortality and avoidance behaviour), and aquatic bioassays using a soil leachate (Daphnia magna immobilisation and Vibrio fischeri bioluminescence inhibition). The treatment with FeSO4 1 % w/w was able to reduce extractable As in soil, but increased the extractable Cu, Mn and Zn concentrations, as a consequence of the decrease in soil pH, in relation to the unamended soil, from 5.0 to 3.4, respectively. As a consequence, this treatment had a detrimental effect in some of the soil enzymatic activities (e.g. dehydrogenase, acid phosphatase, urease and cellulase), did not allow plant growth, induced E. fetida mortality in the highest concentration tested (100 % w/w), and its soil leachate was very toxic towards D. magna and V. fischeri. The combined application of FeSO4 1 % w/w with other treatments (e.g. CaCO3 1 % w/w and paper mill 1 % w/w) allowed a decrease in extractable As and metals, and a soil pH value closer to neutrality. As a consequence, dehydrogenase activity, plant growth and some of the bioassays identified those as better soil treatments to this type of multi-contaminated soil.

Evaluation of the ecotoxicity of pollutants with bioluminescent microorganisms

This chapter deals with the use of bioluminescent microorganisms in environmental monitoring, particularly in the assessment of the ecotoxicity of pollutants. Toxicity bioassays based on bioluminescent microorganisms are an interesting complement to classical toxicity assays, providing easiness of use, rapid response, mass production, and cost effectiveness. A description of the characteristics and main environmental applications in ecotoxicity testing of naturally bioluminescent microorganisms, covering bacteria and eukaryotes such as fungi and dinoglagellates, is reported in this chapter. The main features and applications of a wide variety of recombinant bioluminescent microorganisms, both prokaryotic and eukaryotic, are also summarized and critically considered. Quantitative structure-activity relationship models and hormesis are two important concepts in ecotoxicology; bioluminescent microorganisms have played a pivotal role in their development. As pollutants usually occur in complex mixtures in the environment, the use of both natural and recombinant bioluminescent microorganisms to assess mixture toxicity has been discussed. The main information has been summarized in tables, allowing quick consultation of the variety of luminescent organisms, bioluminescence gene systems, commercially available bioluminescent tests, environmental applications, and relevant references.