Fischeri Bioluminescence Research Articles

Parameters Optimization for Improving Bioluminescence Inhibition Assay Using Vibrio fischeri Bacteria to Detect Lipopolysaccharide Toxicity in Aquatic Environments.

Bioluminescence inhibition of Vibrio fischeri is a widely used method for toxicity testing in aquatic environments. Certain complex biological contaminants, such as lipopolysaccharide (LPS), can interfere with metabolic pathways during toxicity assays. The standard 15-minute Vibrio fischeri bioluminescence assay has limitations when evaluating and screening water toxicity against complex and emerging chemicals like LPS. To accurately determine the effects of such substances, it is crucial to use a bioassay that encompasses a sufficient cell cycle period. This study tested LPS at varying incubation times (ranging from 60s to 60min) and concentrations (1-1*10- 12 mg/ml) to identify the appropriate incubation time for bioluminescence inhibition and toxicity testing. The results indicated that bioluminescence inhibition begins within 60s and reaches maximum inhibition at 60min. However, at 30 and 45min, the bacterial response to different concentrations of LPS varied, with some concentrations causing increased bioluminescence. The EC50 values at different times (60s, 15, 30, 45, and 60min) were found to be 0.0012, 0.0063, 4.07e + 54, 3.85e-8, and 3.34e-9mg/ml respectively. This study highlights the importance of considering incubation time when using bioluminescence inhibition to detect acute toxicity in aquatic ecosystems. A longer incubation time may enhance the method's sensitivity and improve its ability to detect low levels of toxins, such as LPS, in water resources.

Identification of polar bioactive substances in the Upper Rhine using effect-directed analysis

Effect-Directed Analysis (EDA) was used to identify bioactive compounds in surface and well water from the Upper Rhine, and to evaluate their properties against the criteria set for Persistent, Mobile and Toxic (PMT) and very persistent and very mobile (vPvM) substances. A multi-layered solid-phase extraction was implemented to enrich a broad range of polar substances from the collected samples. The extracts were fractionated into 108 fractions and tested in the transthyretin (TTR)-binding assay measuring displacement of fluorescently labeled thyroxine (FITC-T4 TTR-binding assay) and the Aliivibrio fischeri bioluminescence (AFB) bioassay. Bioactive fractions guided the identification strategy using high-resolution mass spectrometry. Chemical features were systematically annotated using library databases and suspect lists, incorporating an automated assessment of the quality of each annotation. Based on this assessment, each chemical feature was assigned a specific identification confidence level. Identification of bioactive compounds was facilitated by using bioassay specific suspect lists that were extracted from an in-house developed database of positive and negative TTR-binding compounds and from a recently published database of active inhibitors of AFB. This resulted in the identification and confirmation of ten bioactive substances, including four evaluated as PMT and vPvM substances (diclofenac, trifloxystrobin acid, 6:2 FTSA and PFOA), and one as a potential PMT substance (4-aminoazobenzene). This study demonstrates the effectiveness of EDA in the identification of PMT/vPvM substances in the aquatic environment, facilitating their prioritization for comprehensive environmental risk assessment and possible regulation.

Application of a laccase-catalyzed oxidative coupling for the removal and detoxification of typical flotation reagent salicylhydroxamic acid

Residual organic flotation reagents in mineral processing wastewater (MPW) can pose environmental hazards and hinder the sustainable development of the mining industry. Laccase as a versatile biocatalyst can eliminate various recalcitrant contaminants from the environment, but its potential applications for the removal and detoxification of organic flotation reagents have until now been overlooked. Herein, the influence of superparamagnetic immobilized laccase (SPM-IMLac) on the enzymatic removal of salicylhydroxamic acid (SHA), a typical mineral flotation reagent, as well as the mechanism of this process have been explored for the first time. The results indicated that SPM-IMLac can effectively remove SHA over a broad pH range and this process follows the pseudo-first-order reaction kinetics. A methodology which combined high resolution mass spectrometry (HRMS) and a solid phase extraction (SPE) technique revealed that SPM-IMLac could catalyze a single-electron oxidation of SHA to generate self/cross-oligomers via radical-driven C-C and/or C-O-C covalent coupling pathways. The Vibrio fischeri bioluminescence inhibition assay and a total organic carbon (TOC) analysis corroborated that the SHA transformation was accompanied by detoxification and by a reduction in TOC of the reaction solution, the extent of which correlated with the extent of the oxidative coupling. Moreover, SPM-IMLac could be easily recovered and reused, while keeping its high removal efficiency of SHA in the actual MPW matrices. This study not only provides fascinating insights into the transformation mechanisms and environmental fate of SHA mediated by SPM-IMLac, but it also exploits a viable and sustainable approach for the remediation of organic flotation reagents-contaminated MPW.

Winter indoor air quality in traditional Mongolian yurts, in a Ger district of Ulaanbaatar

In Ulaanbaatar roughly 60 % of the population live in traditional Mongolian yurts in the so-called Ger districts of the city. Winter indoor air quality is a serious concern in these districts as about 98 % of households consume solid fossil fuel (mainly coal). In our study, indoor air quality was assessed based on PAHs analysis and ecotoxicity testing of 24-hour samples collected in 4 yurts. Three of the selected yurts were equipped with conventional while the fourth one with improved stoves. Analysis of PAHs profiles showed the prevalence of higher molecular weight PAHs in all yurts. Concentrations of the 5-ring benzo(b)fluoranthene and 6-ring benzo(g.h.i)perylene were extremely high in one yurt using conventional stove, 8430 µg g−1 and 6320 µg g−1, respectively. Ecotoxicity of the samples was assessed using the kinetic version of the Vibrio fischeri bioluminescence inhibition bioassay. In concordance with PAHs concentrations, ecotoxicity was also the highest in that yurt.

Nitrogen-reliant degradation behaviors of characteristic NHCs by UV-based advanced oxidation processes: Kinetics, pathways and toxicity assessment

In recent decades, nitrogen-containing heterocyclic compounds (NHCs) have been widely synthesized and applied due to their excellent coordination capability of heterocyclic N atoms. However, their high toxicity and poor biodegradability pose significant hazards to aquatic ecosystems. Three characteristic NHCs (cNHCs) with similar molecular structures but minor differences in the number and position of N atoms, namely benzotriazole (BTA), benzimidazole (BMZ), and indazole (IDZ), were selected to evaluate impacts of these differences on their degradation behaviors during UV/H2O2 treatments. It was found that the key mechanism for the removal of BTA, BMZ, and IDZ in the UV/H2O2 processes was the generation of ∙OH through UV-excited H2O2 decomposition. Density functional theory (DFT) calculations revealed that the variation in the number and position of heterocyclic ring N atoms significantly affected the electron cloud distribution of the cNHCs, thereby resulting in different reactivities. Mineralization results and N evolution experiments indicated that N elements were initially released in the form of ammonia nitrogen during UV/H2O2 treatments, which then underwent oxidation to form nitrite and nitrate. The two ortho-N atoms were most easily mineralized and release inorganic nitrogen, followed by the two meta-N atoms. However, the BTA compound containing three N atoms, exhibited inertness towards radicals after hydroxylation, thereby hindering mineralization. A dual-directional transformation products (TPs) identification protocol was employed to identify 30 TPs of the cNHCs and propose recommended degradation pathways. Furthermore, Vibrio fischeri bioluminescence inhibition bioassay and QSAR prediction models were used to preliminarily screen and identify 13 toxic TPs with potential ecological risks.

Assessing the genotoxic potential of wastewater effluents from three wastewater treatment plants in South Africa.

Wastewater treatment plants are mainly monitored for quality in terms of their biological oxygen demand and microbiological constituents as stipulated in the specific discharge permit. Wastewater influents and effluents were taken from three WWTPs in South Africa over the summer and winter seasons. Previous toxicity tests such as the Vibrio fischeri bioluminescence assay and the Selenastrum capricornutum algal growth inhibition test have shown that the effluents displayed acute toxicity. To further investigate the quality of the effluent, the genotoxic potential was determined using the SOS Chromosome and UMU Chromosome test. The SOS Chromotest demonstrated induction factor values of above 1.5 for influents during both seasons indicating that the influents were genotoxic (p < 0.05). Effluents discharged during winter and summer also had induction factors greater than 1.5 (p < 0.05). A range of induction factors was detected with the UMU-Chromotest for influents and effluents (1.98 ± 0.38 and 2.40 ± 0.51, respectively). Findings show point sources in the area can lead to influents and effluents that are potentially genotoxic. Designing a monitoring programme that encompasses testing of both the regulatory determinants with additional specialized tests can provide a more holistic view of wastewater quality and the efficiency of WWTP to reduce the discharge of hazards.

Effect of sulfur on the solar light photoactivity of TiO2-based photocatalysts

Crude TiO2 derived from sulfate technology was used as a precursor for the novel solar light active photocatalysts with various sulfur content (S-TiO2). The effect of sulfur on the physicochemical properties of S-TiO2 and efficiency of ketoprofen photodecomposition under simulated solar light was investigated. Additionally, the activity of selected photocatalysts was evaluated under visible light and UV radiation. Moreover, different scavengers were applied to explore the mechanism of ketoprofen decomposition. Furthermore, the acute toxicity tests were performed to assess a toxicological effect of the decomposition products. It was proved that the sulfur content in a range of ∼ 0.7–1.2 wt% was a key factor affecting the photoactivity under simulated solar light. The most beneficial sulfur content was ∼ 0.9 wt%. It was revealed that the solar light induced photoactivity of the examined photocatalysts derived mainly from the visible light photocatalysis mechanism, with some contribution of the UV photocatalysis mechanism. The most important oxidizing species were h+, O2⦁− and ⦁OH, and among them h+ had the greatest impact under solar and visible light irradiation. However, the influence of e- cannot be disregarded. Based on the Aliivibrio fischeri bioluminescence assay a significant influence of the irradiation type on the treated solution toxicity was found.

Nighttime–daytime PM10 source apportionment and toxicity in a remoteness inland city of the Iberian Peninsula

The distribution of daytime and nighttime sources of PM10 collected from January to March 2021 at an urban background site in the city of Bragança, Portugal, was performed using positive matrix factorisation (PMF). Additional data of PM2.5, NOx and meteorological variables were collected to support the interpretations. A solution with 5 factor profiles was found: traffic (33%), dust (24%), biomass burning (21%), secondary inorganic aerosol (SIA) (12%) and sea salt (10%). Mean daytime and nighttime PM10 concentrations were 43.1 μg m−3 and 46.1 μg m−3, respectively. Nighttime concentrations were dominated by residential biomass combustion. Vehicle traffic and dust factors showed significantly greater contributions during the day (+12% and +4%, respectively), suggesting that exhaust and non-exhaust emissions and long-range transport are important contributors to daytime PM10 levels. In contrast, there were no significant differences between day and night for SIA and sea salt. Exceedances of the daily limit to PM10 (50 μg m−3) and PM2.5 (15 μg m−3) were observed in 22 (33%) and 27 (40%) days of the campaign, respectively, mostly associated with biomass burning for residential heating, but also with Saharan dust outbreaks. The application of the Aliivibrio fischeri bioluminescence inhibition assay for ecotoxicity assessment allowed classifying 70% of the samples as toxic, especially those from the nocturnal period, indicating that biomass burning is one of the main sources responsible for PM10 toxicity. Both the contributions from biomass burning estimated by the PMF and multiple tracers of this source showed statistically significant correlations with the toxicity units.

Ecotoxicity attenuation by acid-resistant nanofiltration in scandium recovery from TiO2 production waste

The lack of high-grade scandium (Sc) ores and recovery strategies has stimulated research on the exploitation of non-ore-related secondary sources that have great potential to safeguard the critical raw materials supply of the EU's economy. Waste materials may satisfy the growing global Sc demand, specifically residues from titanium dioxide (TiO2) production. New technologies are being developed for the recovery of Sc from such residues; however, the possible environmental impacts of intermediary products and residues are usually not considered. In order to provide a comprehensive ecotoxicity characterisation of the wastes and intermediate residues resulting from one promising new technology, acid-resistant nanofiltration (arNF), a waste-specific ecotoxicity toolkit was established. Three ecotoxicity assays were selected with specific test parameters providing the most diverse outcome for toxicity characterisation at different trophic levels: Aliivibrio fischeri (bacteria) bioluminescence inhibition (30 min exposure), Daphnia magna (crustacean) lethality and immobilisation (24 h exposure) and Lemna minor (plant) growth inhibition with determination of the frond number (7 d exposure). According to our results, the environmental impact of the generated intermediate and final residues on the aquatic ecosystem was mitigated by the consecutive steps of the filtration methods applied. High and statistically significant toxicity attenuation was achieved according to each test organism: toxicity was lowered based on EC20 values, according to the A. fischeri bioluminescence inhibition assay (by 97%), D. magna lethality (by 99%) and L. minor frond number (by 100%), respectively, after the final filtration step, nanofiltration, in comparison to the original waste. Our results underline the importance of assessing chemical technologies' ecotoxicological and environmental impacts with easy-to-apply and cost-effective test methods to showcase the best available technologies.

Characteristics of particle-bound polycyclic aromatic hydrocarbons (PAHs) in indoor PM2.5 of households in the Southwest part of Ulaanbaatar capital, Mongolia

Air pollution, including PM2.5 concentration in Ulaanbaatar (capital of Mongolia) is a serious matter of concern. As the majority of households use coal in large areas of the city, indoor air quality is also posing a serious risk to human health. This study investigated the concentration of polycyclic aromatic compounds (PAHs) in indoor particulate matter (PM2.5) in 10 non-smoker households. Sampling was conducted in winter of 2018, between 27 January and 09 February. Concentrations of PM2.5 in the indoor air of households ranged between 62.8 and 324.8 µg m−3. Total concentration of PAHs also varied in a relatively wide range, between 46.2 and 175.7 ng m−3. Five-ring PAHs represented a considerably high fraction of total PAHs between 25 and 53%, benzo[b]fluoranthene (BbF) and benzo[a]pyrene (BaP) were the two predominant compounds within five-ring PAHs. Significant correlation was found between indoor and outdoor particulate matter levels in wintertime. Considering individual characteristic PAHs, heavier PAHs homologues (4- to 5-ring and 6-ring PAHs) were detected in all households, which suggested the influence of coal combustion and traffic exhaust. Health risk of children attributed to PAHs inhalation was assessed by taking into account the lifetime-average daily dose (LADD) and corresponding lifetime cancer risk. Lifetime average daily dose for children in only one household were slightly higher than health-based guideline level (1.0 × 10−5), defined by WHO, whereas LADD for adults and children of other households were within acceptable limit. The cancer risks from the exposure of children to air pollutants in all households except HH-3 were found high. In the Vibrio fischeri bioluminescence inhibition assay, according to the toxic unit (TU) values of indoor PM2.5 from ten households, all samples were classified as toxic.

Outdoor charcoal grilling: Particulate and gas-phase emissions, organic speciation and ecotoxicological assessment

Charbroiling is a major source of air pollution worldwide. In this study, the particulate and gas-phase emissions from the charcoal lighting phase and during the grilling of meat (pork and rump cap) and fish (sardine and salmon) on an outdoor barbecue grill were characterized. Some gaseous compounds (ethane, hexane, NO2, N2O, SO2, NH3, HCl) did not display significant variations between samples and the background level, indicating that they are not emitted during barbecuing. During the charcoal heating phase, levels of total volatile organic compounds (TVOCs) increased 6 times above the background value. Four-to 5-fold increases in TVOC concentrations were observed when grilling sardines and salmon, while rises of 1.3–1.5 were recorded for meat. Emission factors of 32.4 g PM10 kg−1 and 22.7 g TVOCs kg−1 were obtained for the biofuel ignition phase. PM10 emission rates of 472, 531, 1104 and 918 mg kg−1 were estimated for pork, rump cap, sardine and salmon charbroiling, respectively. TVOC emissions ranged from 23.9 mg kg−1 (pork) to 82.6 mg kg−1 (salmon). Organic carbon accounted for 35.0% of the PM10 emitted during the ignition and flaming phases of the biofuel but represented mass fractions of 56–64% of the particulate emissions during food charbroiling. About 235 organic compounds were quantified in the PM10 samples. The ecotoxicity was assessed using the kinetic version of the Vibrio fischeri bioluminescence inhibition bioassay. All samples were classified as very toxic or toxic. Ecotoxicity was statistically correlated with several n-alkanes, PAHs and alkyl-PAHs, anhydrosugars, acids, and phenolic compounds.

Insight into BDD electrochemical oxidation of florfenicol in water: Kinetics, reaction mechanism, and toxicity

Antibiotics in the environment provoke serious consequences on living beings and can be effectively remediated by prominent advanced oxidation process. In this study, electrochemical advanced oxidation treatment in a lab-scale reactor for the degradation of florfenicol (FLO) was studied with the aid of boron-doped diamond anode (BDD). The results exhibited that the FLO degradation follows pseudo-first-order kinetics. As the current intensity rose from 60 mA to 250 mA, the FLO removal efficiency increased and the corresponding reaction rate constant increased from 0.0213 to 0.0343 min−1, which was likely due to the more efficient participation of free hydroxyl radical (•OH) generated at the BDD anode. Faster degradation and higher mineralization of electrolyzed FLO solution were achieved at higher current intensity as well as in higher SO42− concentration medium, as a consequence of catalytic participation of oxidants (free •OH as well as sulfate radical (SO4•−) and persulfate (S2O82−)). The increase in FLO concentration from 30 to 50 mg L−1 resulted in a reaction rate constant decrease (from 0.0235 to 0.0178 min−1). Eight transformation by-products (m/z = 372.99, 359.8, 338.0, 324.04, 199.00, 185.02, 168.99 and 78.989) and three inorganic ions (NO3−, Cl− and F−) were analyzed by UPLC‒Q‒TOF‒MS/MS and Ion‒chromatography, respectively. The Vibrio fischeri bioluminescence inhibition revealed an increase of toxicity during the electrochemical oxidation that could be attributed mostly to the generated organic chlorinated by-products (m/z = 372.99, 359.8) and inorganic species (ClO2− and ClO3−).

Dimension-reduction simplifies the analysis of signal crosstalk in a bacterial quorum sensing pathway

Many pheromone sensing bacteria produce and detect more than one chemically distinct signal, or autoinducer. The pathways that detect these signals are typically noisy and interlocked through crosstalk and feedback. As a result, the sensing response of individual cells is described by statistical distributions that change under different combinations of signal inputs. Here we examine how signal crosstalk reshapes this response. We measure how combinations of two homoserine lactone (HSL) input signals alter the statistical distributions of individual cell responses in the AinS/R- and LuxI/R-controlled branches of the Vibrio fischeri bioluminescence pathway. We find that, while the distributions of pathway activation in individual cells vary in complex fashion with environmental conditions, these changes have a low-dimensional representation. For both the AinS/R and LuxI/R branches, the distribution of individual cell responses to mixtures of the two HSLs is effectively one-dimensional, so that a single tuning parameter can capture the full range of variability in the distributions. Combinations of crosstalking HSL signals extend the range of responses for each branch of the circuit, so that signals in combination allow population-wide distributions that are not available under a single HSL input. Dimension reduction also simplifies the problem of identifying the HSL conditions to which the pathways and their outputs are most sensitive. A comparison of the maximum sensitivity HSL conditions to actual HSL levels measured during culture growth indicates that the AinS/R and LuxI/R branches lack sensitivity to population density except during the very earliest and latest stages of growth respectively.

Morphological properties, chemical composition, cancer risks and toxicological potential of airborne particles from traffic and urban background sites

From a sampling campaign from December 2018 to June 2019, at a traffic and an urban background site in Coimbra, Portugal, two particulate matter (PM10) samples from each month were selected to characterise the morphology by scanning electron microscopy, to determine the organic and inorganic chemical composition by multiple analytical techniques and to assess the ecotoxicity by the Vibrio fischeri bioluminescence inhibition assay. PM10 concentrations in winter were approximately twice as high as those recorded in the spring. Biomass burning was the greatest contributor to air pollution in winter at both sites. The contribution of vehicle emissions to the PM10 at the roadside was, on average, 7 times higher than at the background location. Distinct particle morphologies were observed. Higher abundances of aggregates enriched in Fe, Ti, Ba, Cr, Co, Cu, Zr, Mn and soot particles were registered in samples from the roadside. Bivariate plots suggested common sources of PAHs, mostly traffic and biomass burning, across the city. Benzo[a]pyrene equivalent concentrations were within the values documented for other European cities. Cancer risks resulting from exposure to PAHs by inhalation were estimated to be low (10−6 ≤ to <10−4) for both sites. The noncarcinogenic risks from particulate trace elements were always higher than the target value of 1. Cancer risks for Cr were found to be higher than the acceptable level (10−6). The calculation of toxic units indicated that 64% of the samples from the roadside location were toxic and 14% very toxic, while the corresponding shares for the urban background site were 50% and 7%, respectively. Many PM10-bound constituents, especially markers of biomass burning (e.g. anhydrosugars) and traffic emissions (e.g. Fe, Cu, Zn), showed significant statistical correlations with toxicity.

In vitro toxicity of particulate matter emissions from residential pellet combustion

Particulate matter emissions (PM10) from the combustion, in a residential stove, of two commercial brands of certified (ENplus A1) pellets, a non-certified brand and laboratory made pellets of acacia were tested for their ability to induce ecotoxic, cytotoxic, and mutagenic responses in unicellular organisms and a human cell line. Ecotoxicity was evaluated through the Vibrio fischeri bioluminescence inhibition assay. Moreover, cytotoxicity was assessed at two time points (24- and 48-hr) through two complementary techniques in order to evaluate the cellular metabolic activity and membrane integrity of human lung epithelial cells A549. The Ames test using two Salmonella typhimurium strains (TA100 and TA98) was employed to assess the mutagenic potential of the polycyclic aromatic hydrocarbon fraction extracted from the PM10 samples. Results obtained with the bioluminescent bacteria indicated that only particles from the combustion of acacia pellets were toxic. All samples induced impairment on the A549 cells metabolic activity, while no significant release of lactate dehydrogenase was recorded. PM10 emissions from acacia pellets were the most cytotoxic, while samples from both certified pellets evoked significant cytotoxicity at lower doses. Cytotoxicity time-dependency was only observed for PM10 from the combustion of acacia pellets and one of the brands of certified pellets. Mutagenic activity was not detected in both S. typhimurium strains. This study emphasises the role of the raw material for pellet manufacturing on the toxicological profile of PM emissions. Alternative raw materials should be deeply investigated before their use in pelletisation and combustion in residential appliances.

In vitro toxicity of indoor and outdoor PM10 from residential wood combustion

Particulate matter with aerodynamic diameter < 10 μm (PM10) was collected, indoors and outdoors, when wood burning appliances (open fireplace and woodstove) were in operation. The PM10 ecotoxicity was assessed with the Vibrio fischeri bioluminescence inhibition assay, while the cytotoxicity was evaluated by the WST-8 and lactate dehydrogenase (LDH) release assays using A549 cells. Extracts of PM10-bound polycyclic aromatic hydrocarbons (PAH) were tested for their mutagenicity through the TA98 and TA100 Ames test. The bioluminescent inhibition assay revealed that indoor particles released from the fireplace were the most toxic. Indoors, the reduction in A549 cell metabolic activity was over two times higher for the fireplace in comparison with the woodstove (32 ± 3.2% and 72 ± 7.6% at the highest dose, respectively). Indoor particles from the fireplace were found to induce greater cytotoxicity than the corresponding outdoor samples. Combined WST-8 and LDH results suggest that PM10 exposure induce apoptotic cell death pathway in which the cell membrane integrity is maintained. Indoor and outdoor samples lacked direct and indirect mutagenic activity in any of the tester strains. For indoor-generated PM10, organic carbon and PAH were significantly correlated with cell viability and bioluminescence reduction, suggesting a role of organic compounds in toxicity.

Integration of olive stones in the production of Fe/AC-catalysts for the CWPO treatment of synthetic and real olive mill wastewater

A by-product of olive mill’s operation (olive stone, OS) was transformed into activated carbon (AC) and used as support to prepare Fe-based catalysts, which were employed on the catalytic wet peroxide oxidation (CWPO) of olive mill wastewater (OMW). Three Fe-impregnation routes were tested: incipient wetness impregnation (IWI), adsorption (Ads), and hydrothermal (HT), resulting in catalysts with distinct iron loadings, particle sizes and surface dispersion. OSAC-Fe catalysts were characterized by N2 and CO2 physisorption, XRD, XPS, FTIR, HRTEM, EDX, and HRSEM techniques. Catalysts’ activity and stability was first compared in the degradation of synthetic polyphenolic solutions. After one cycle (240 min), catalysts’ sorption capacity was considerably exhausted and OH radicals were found to be the main oxidative species responsible for total phenolic content (TPh) removal. OSAC-Fe-IWI and OSAC-Fe-Ads performed better than OSAC-Fe-HT after four consecutive cycles (53 and 48 vs. 38% TPh removals, respectively), also showing considerably lower cumulative Fe leaching values (2.2 and 2.8 vs. 10 wt%). The most promising materials were used for depuration of real OMW samples. Under smooth operational conditions ([OSAC-Fe-IWI] = 2.0 g/L, [H2O2] = 0.5 g/L, pH0 ~ 4.9, T0 = 25 °C), 55% TPh removal was attained after 240 min, resulting in a significant reduction of the effluent’s toxicity (from 100% Vibrio fischeri bioluminescence inhibition to 36%), 37% chemical oxygen demand degradation, and 21% total organic carbon mineralization. Promising catalytic performances were also achieved by OSAC-Fe-Ads, despite its considerably lower iron loading, highlighting the importance of Fe surface dispersion.

Toxicity assessment of total petroleum hydrocarbons in aquatic environments using the bioluminescent bacterium Aliivibrio fischeri

Toxicity monitoring of environmental pollutants especially petroleum hydrocarbons as priority pollutants is an important environmental issue. This study addresses a rapid, sensitive and cost effective method for the detection of total petroleum hydrocarbons (TPHs) using Aliivibrio fischeri bioluminescence inhibition bioassay. At the first step, the optimum conditions including time, pH and temperature for growth of A. fischeri were determined. Then, two methods were used to evaluate the toxicity of petroleum compounds. In the first method, short-term (15 min) and long-term (16 h) toxicity assays were performed. In the second method luminescence kinetics of A. fischeri was investigated during 24 h. The results demonstrated the most appropriate time for the bacterial growth occurred 16 h after inoculation and optimum temperature and pH were found 25 °C and 7, respectively. Short-term and long-term toxicity did not indicate any toxicity for various concentrations of TPHs (30, 50, 110, 160, 220 mg/L). Considering the luminescence kinetics of A. fischeri the long-term assay was introduced as 6 h. The half maximal effective concentration (EC50) was achieved 1.77 mg/L of TPHs. It is concluded that the luminescence kinetics of A. fischeri can be a valuable approach for assessing toxicity of TPHs in aquatic environments.

Degradation of acesulfame in UV/monochloramine process: Kinetics, transformation pathways and toxicity assessment

UV/monochloramine (UV/NH2Cl) is an emerging advanced oxidation process that can generate various reactive species like reactive chlorine species (RCS) and hydroxyl radicals for micropollutant removal. This study investigated the potential toxicity of transformation products resulting from UV/NH2Cl treatment of acesulfame (ACE), as an example of micropollutant, found in worldwide aquatic environment. Compared with UV photolysis and chloramination, the UV/NH2Cl process more effectively degraded ACE. The transformation products of ACE treated with the UV/NH2Cl process were identified and characterized with high resolution mass spectrometry. The formation of chlorinated-TPs indicated the role of RCS in UV/NH2Cl transformation even though UV photolysis was predominantly responsible for the ACE degradation. The Vibrio fischeri bioluminescence inhibition assay revealed a higher toxicity of TPs derived from UV/NH2Cl than from UV photolysis. The increased toxicity could be attributed to most of the generated chlorinated-TPs (Cl-TPs), in particular those halo-alcohols. The ECOSAR program predicts that halo-alcohol TPs are more toxic than their non-chlorinated analogues and other Cl-TPs. This study provides insight into the important role of reactive species in the micropollutants’ transformation of UV/NH2Cl process. It further provides information relevant to the potential risk when applying the process for micropollutant removal in water treatment.

Assessment of the potential bactericide effect of self-cleaning floors: a proposed protocol.

The antibacterial properties of self-cleaning coatings are based on bactericide nanoparticles (NPs). Ecotoxicity of these NPs have been assessed mostly in suspension, using standard bioassays. Here a protocol is proposed to test actual coating samples, using the Vibrio fischeri bioluminescence inhibition bioassay. The protocol was designed to test bactericide properties of specially coated PVC floors being used in hospital environments under quasinatural conditions, such as prolonged exposure or room temperature. To take into consideration that the light output of the bacteria under prolonged exposure naturally changes, a correction factor is proposed.