Effect of dust on the viability of Vibrio fischeri in the Microtox Test

Cellular Responses Induced by Zinc in Zebra Mussel Haemocytes. Loss of DNA Integrity as a Cellular Mechanism to Evaluate the Suitability of Nanocellulose-Based Materials in Nanoremediation

Zinc environmental levels are increasing due to human activities, posing a threat to ecosystems and human health. Therefore, new tools able to remediate Zn contamination in freshwater are highly recommended. Specimens of Dreissena polymorpha (zebra mussel) were exposed for 48 h and 7 days to a wide range of ZnCl2 nominal concentrations (1-10-50-100 mg/L), including those environmentally relevant. Cellulose-based nanosponges (CNS) were also tested to assess their safety and suitability for Zn removal from freshwater. Zebra mussels were exposed to 50 mg/L ZnCl2 alone or incubated with 1.25 g/L of CNS (2 h) and then removed by filtration. The effect of Zn decontamination induced by CNS has been verified by the acute toxicity bioassay Microtox®. DNA primary damage was investigated by the Comet assay; micronuclei frequency and nuclear morphological alterations were assessed by Cytome assay in mussels' haemocytes. The results confirmed the genotoxic effect of ZnCl2 in zebra mussel haemocytes at 48 h and 7-day exposure time. Zinc concentrations were measured in CNS, suggesting that cellulose-based nanosponges were able to remove Zn(II) by reducing its levels in exposure waters and soft tissues of D. polymorpha in agreement with the observed restoration of genetic damage exerted by zinc exposure alone.

Comparison of UV/Persulfate and UV/H2O2 for the removal of naphthenic acids and acute toxicity towards Vibrio fischeri from petroleum production process water

The ultraviolet light-activated persulfate process (UV/Persulfate) has received much attention in recent years as a novel advanced oxidation method for the treatment of municipal and industrial wastewater. This work investigated the UV/Persulfate and UV/H₂O₂ processes for the treatment of real oil sands process water (OSPW) at ambient pH condition using a medium pressure mercury lamp (emission between 200 and 530 nm). The degradation performances towards fluorophore organic compounds and naphthenic acids (NAs) in OSPW were evaluated using synchronous fluorescence spectrometry and ultra performance liquid chromatography time-of-flight mass spectrometry, respectively. Compared to the UV/H₂O₂ process, the UV/Persulfate process exhibited higher efficiency to remove both NAs and fluorophore organic compounds. Under 40 min of UV exposure and incident irradiance of 3.50 mW cm^-2, fluorophore organic compounds were greatly degraded by UV/Persulfate (2 mM) and two- and three-ring fused organics were completely removed. 59.4%, 83.8% and 92.2% of O₂-NAs in OSPW were removed with persulfate dosages of 0.5, 2, and 4 mM, respectively. The removal efficiency decreased along with the number of oxygen atoms in NAs (83.8%, 49.3%, and 46.8% for O₂-, O₃-, and O₄-NAs, respectively) with 2 mM of persulfate, because of the formation of oxidized NAs in the same process. The structure-reactivity of O₂-NA compounds fitted pseudo-first order kinetics in UV/Persulfate process with the rate constants ranging from 0.0156 min^-1 to 0.1511 min^-1. NAs with higher carbon numbers and double bond equivalence were more reactive in the UV/Persulfate oxidation process. The acute toxicity of OSPW to Vibrio fischeri was significantly reduced after the UV/Persulfate and UV/H₂O₂ treatments. Overall results demonstrated that the UV/Persulfate oxidation can be an effective alternative for future reclamation of OSPW.

Characterization of polar metabolites and evaluation of their potential toxicity in hydrocarbon contaminated Antarctic soil elutriates

Hydrocarbon polar metabolites are gaining interest from industry and the remediation community due to their ubiquity and uncertainty around their toxicity. In this study, we used headspace-gas chromatography/mass spectrometry (HS-GC/MS) to characterize polar metabolites present in elutriates derived from uncontaminated, freshly hydrocarbon contaminated and partially remediated Antarctic soils. Elutriates represent the bioavailable fraction and may be used as a proxy for leachate runoff in environmental risk assessments. Control and contaminated soil elutriates were analysed for the presence of 12 aldehydes and two ketones, which cover a broad spectrum of metabolites, ranging from nC₂ - nC₁₂ carbon chain length. A total of nine aldehydes were detected in the soil elutriates. Types of aldehydes present in uncontaminated and hydrocarbon contaminated elutriates were similar. Among the polar metabolites measured in elutriates, acetaldehyde was most abundant in partially remediated soils. Microtox assays were used to determine the potential toxicity of elutriates. In addition, three aldehydes that were present at the highest concentrations in the contaminated and partially remediated soil elutriates (acetaldehyde, octanal and undecanal) were tested as single compounds. Contaminated soil elutriates tested were found to be toxic, with partially remediated elutriates less toxic than freshly contaminated elutriates. None of the three aldehydes tested separately were toxic at levels at which they were measured in elutriates. We infer that high levels of acetaldehyde in partially remediated soil due to hydrocarbon degradation highlight the potential of this metabolite as a useful chemical marker for hydrocarbon degradation under certain conditions. Microtox was sensitive to metabolites and provided a useful initial screening tool for elutriates.

Proposed method for controlling turbid particles in solid-phase bioluminescent toxicity measurement

In the recent half century, numerous methods have been developed to assess ecological toxicity. However, the presence of solid-particle turbidity sometimes causes such tests to end with questionable results. Many researchers focused on controlling this arbitrary turbidity effect when using the Microtox® solid-phase toxicity system, but there is not yet a standard method. In this study, we examined four solid-phase sample test methods recommended in the Microtox® manual, or proposed from the literature, and compared the existing methods with our proposed method (centrifuged basic solid-phase test, c-BSPT). Four existing methods use the following strategies to control turbid particles: complete separation of liquid and solid using 0.45-μm filtration before contacting solid samples and bacteria, natural settlement, moderate separation of large particles using coarser pore size filtration, and exclusion of light loss in the toxicity calculation caused by turbidity after full disturbance of samples. Our proposed method uses moderate centrifugation to separate out the heavier soil particles from the lighter bacteria after direct contact between them. Among the solid-phase methods tested, in which the bacteria and solid particles were in direct contact (i.e., the three existing methods and the newly proposed one, c-BSPT), no single method could be recommended as optimal for samples over a range of turbidity. Instead, a simple screening strategy for selecting a sample-dependent solid-phase test method was suggested, depending on the turbidity of the solid suspension. The results of this study highlight the importance of considering solid particles, and the necessity for optimal selection of test method to reduce errors in the measurement of solid-phase toxicity.

Antiproliferative activity against human tumor cell lines and toxicity test on Mediterranean dietary plants

Sixteen edible plants from Southern Italy were evaluated for their in vitro antiproliferative properties, using the sulforodamine B (SRB) assay, on four human cancer cell lines: breast cancer MCF-7, prostate cancer LNCaP, amelanotic melanoma C32 and renal adenocarcinoma ACHN. After 48 h of incubation the most antiproliferative plant extract was Cynara cardunculus ssp. cardunculus on C32 and ACHN cell lines with IC(50) of 21 and 18 microg/ml, respectively. Mentha aquatica showed a selective antiproliferative activity on breast cancer while significant activity was exerted by Cichorium intybus on melanoma. These species contained the highest amount of phenolics. The acute toxicity of the hydroalcohol extracts from all the plants were evaluated by using the Microtox acute toxicity test. This bacterial test measures the decrease in light emission from the marine luminescent Vibrio fischeri bacteria when exposed to organic extracts. This inhibition test was revealed to be highly sensitive, cost effective and easy to operate, requiring just 15 min to predict the sample toxicity. All the extracts analyzed resulted to give values very less than a limit of 20% value, demonstrating so an irrelevant toxicity for the human health. In contrast, Echium vulgare and Malva sylvestris showed bioluminescence inhibition values of 19.42% and 17.32%, respectively, just under the established limit.

Effects of mycotoxins, aflatoxin B1 and deoxynivalenol, on the bioluminescence of Vibrio fischeri

The effects of aflatoxin B1 and deoxynivalenol on the luminescence of Vibrio fischeri were investigated to determine the conditions of using the bioluminescence as an indirect means for mycotoxin detection. The culture of Vibrio fischeri showed that bioluminescence reached a peak after 12 hours of incubation at 25 °C and then decreased drastically. During the lag phase which lasted 6 hours, light emission decreased drastically for both the mycotoxin assays – aflatoxin B1 10 µg/ml and deoxynivalenol 20 µg/ml – and the corresponding controls. Distinct bioluminescence inhibition appeared after this period of minimal bioluminescence of the controls and started with the exponential phase of growth. The percentage of bioluminescence inhibition for both mycotoxins was determined after 3.5, 10, 15 and 25 hours of incubation. The bioluminescence of Vibrio fischeri was inhibited with aflatoxin B1 and enhanced with deoxynivalenol. Both effects were delayed and required a long-term incubation over 10 hours, which may help to investigate bioassays for mycotoxin detection.

Ecotoxicity, phytotoxicity and extractability of heavy metals from different stabilised sewage sludges

The presence of heavy metals in the sludges produced in wastewater treatment plants restricts their use for agricultural purposes. This study compares different types of sludges (aerobic, anaerobic, unstabilised and sludge from a waste stabilisation pond) in order to assess the extractability of heavy metals using simple extraction, water and DTPA. The stabilisation treatment undergone by the sludges influenced the heavy metals extractability. The least mineralised sludges (unstabilised and aerobic) showed higher metal extractability. The sewage sludges were subjected to chemical characterisation and toxicity testing (ecotoxicity and phytotoxicity assays) in absence of substrate, to provide a preliminary assessment of their suitability for land application. The ecotoxicity assays confirmed that no sludge constituted a hazardous waste. The sludge extracts had significant adverse effect on the germination index (GI) of barley (Hordeum vulgare L.) and cress (Lepidium sativum L.), a fact which indicates that some characteristics affected root growth.

Evaluation of the toxicity of two soils from Jales Mine (Portugal) using aquatic bioassays

Soil contamination can be one path for streams and groundwater contamination. As a complement of chemical analysis and total contaminants determination, bioassays can provide information on the bioavailable fraction of chemical compounds, focusing on the retention and habitat function of soils. In this study the evaluation of the toxicity of two soils from the abandoned Jales Mine (Portugal) regarded both functions. The buffer capacity of soils was tested with bioassays carried out using the cladoceran Daphnia magna and the marine bacteria Vibrio fischeri. The habitat function of soils was evaluated with the reproduction bioassay with the collembolan Folsomia candida. The Microtox solid-phase test was performed with V. fischeri using soil as test medium, and soil elutriates were extracted to perform the Microtox basic test, and an immobilization and reproduction bioassay with D. magna. The marine bacteria showed high sensitivity to the soil with low heavy metal content (JNC soil) and to JNC soil elutriates, while the soil with highest heavy metal content (JC soil) or soil elutriates exposure did not cause any toxic effect. In the bioassays with D. magna, organisms showed sensitivity to JNC and also to JC soil elutriates. Both mobilization and reproduction features were inhibited. The bioassay with F. candida did not reflect any influence of the contaminants on their reproduction. Although JNC soil presented lower heavy metal contents, elutriates showed different patterns of contamination when compared to JC soil and elutriates, which indicates different retention and buffer capacities between soils. Results obtained in this study underlined the sensitivity and importance of soil elutriate bioassays with aquatic organisms in the evaluation strategy in soil ERA processes.