Olivine avoidance behaviour by marine gastropods (Littorina littorea L.) and amphipods (Gammarus locusta L.) within the context of ocean alkalinity enhancement.

Gigaton scale atmospheric carbon dioxide (CO2) removal (CDR) is needed to keep global warming below 1.5 °C. Coastal enhanced olivine weathering is a CDR technique that could be implemented in coastal management programmes, but its CO2 sequestration potential and environmental safety remain uncertain. Large scale olivine spreading would change the surficial sediment characteristics, which could potentially reduce habitat suitability and ultimately result in community composition changes. To test this hypothesis, we investigated the avoidance response of the marine gastropod Littorina littorea (Linnaeus, 1758) and marine amphipod Gammarus locusta (Linnaeus, 1758) to relatively coarse (83 - 332 µm) olivine and olivine-sediment mixtures during short-term choice experiments. Pure olivine was significantly avoided by both species, while no significant avoidance was observed for sediment with 3% or 30% w/w olivine. For L. littorea, aversion of the light green colour of pure olivine (i.e. positive scototaxis) was the main reason for avoidance. Moreover, olivine was not significantly avoided when it was 7.5 cm (45%) closer to a food source/darker microhabitat (Ulva sp.) compared to natural sediment. It is inferred that the amphipod G. locusta avoided pure olivine to reduce Ni and Cr exposure. Yet, a significant increase in whole body Ni concentrations was observed after 79 h of exposure in the 30% and 100% w/w olivine treatments compared to the sediment control, likely as a result of waterborne Ni uptake. Overall, our results are significant for ecological risk assessment of coastal enhanced olivine weathering as they show that L. littorea and G. locusta will not avoid sediments with up to 30% w/w relatively coarse olivine added and that the degree of olivine avoidance is dependent on local environmental factors (e.g. food or shelter availability).

Effect of incubation time of three single extraction procedures on trace element extraction from sediment and soil.

The use of standard single-extraction procedures to evaluate the mobility and availability of trace elements is a common practice in most laboratories dealing with soil or sediment analysis. Most standard single-extraction procedures describe incubations last for 2 h. However, these were tested and validated for soil analysis. Applying them for sediment analysis without further investigation might be misleading and should be reviewed with care. This paper investigates the effect of incubation time on the extraction efficiency of three standard single-extracting reagents (0.01 M CaCl2, 1 M NH4NO3, and 0.05 M EDTA). Incubation experiments with sediment and soil samples lasting for 2 h, 10 h, and 10 d were performed. The results indicated that 2 h appears sufficient to reach equilibrium using CaCl2 or NH4NO3 for soil analysis; but when analyzing sediments, incubation for 10 d resulted in higher concentrations. Incubation experiments with 0.05 M EDTA showed that incubation for 2 h was enough to extract Cd from the soil sample, Mn and to a lesser extent Cd from the sediment samples; while for the other elements, incubation for 10 d yielded higher concentrations for both sample types compared to that obtained after 2 h and 10 h separately. Relative to the pseudo-total metal contents, more than 55% of all studied elements were extracted by using 0.05 M EDTA, indicating high bioavailable metal fraction.

Arabidopsis root growth and development under metal exposure presented in an adverse outcome pathway framework.

Due to human activities, soils become more and more polluted with metals, which imposes risks for human health and wildlife welfare. As most of the metals end up in the food chain through accumulation in plants, we need to establish science-based environmental criteria and risk management policies. To meet these necessities, a thorough understanding is required of how these metals accumulate in and affect plants. Many studies have been conducted towards this aim, but strikingly, only a few entries can be found in ecotoxicological databases, especially on Arabidopsis thaliana, which serves as a model species for plant (cell) physiology and genetic studies. As experimental conditions seem to vary considerably throughout literature, extrapolation or comparison of data is rather difficult or should be approached with caution. Furthermore, metal-polluted soils often contain more than one metal, yet limited studies investigated the impact of metal mixtures on plants. This review aims to compile all data concerning root system architecture under Cu, Cd and Zn stress, in single or multi-metal exposure in A. thaliana, and link it to metal-induced responses at different biological levels. Global incorporation into an adverse outcome pathway framework is presented.

The relevance of European Biota Quality Standards on the ecological water quality as determined by the multimetric macro-invertebrate index: A Flemish case study.

European Biota Quality Standards (EQSbiota), for compounds with low water solubility and high biomagnification, were created to sustain water quality and protect top predators and humans from secondary poisoning. In reality, for multiple compounds, an exceedance of these standards is often reported in literature without a decrease in ecological water quality determined by biotic indices. In the present study, threshold concentrations were defined in biota (from 44 sampling locations throughout Flanders (Belgium)), above which a good ecological water quality, assessed by the Multimetric Macroinvertebrate Index Flanders (MMIF), was never reached. Threshold values were compared to current EQSbiota. Accumulated perfluoroctane sulfonate (PFOS), mercury (Hg), hexabromocyclododecane (HBCD), polybrominated diphenyl ethers (PBDEs), dioxins and polychlorinated biphenyls (PCBs) concentrations were measured in muscle tissue of European yellow eel (Anguilla anguilla) and perch (Perca fluviatilis). Fluoranthene and benzo(a)pyrene were also analyzed in translocated mussels (Dreissena bugensis, D. polymorpha and Corbicula fluminea). Threshold values could only be calculated using a 90th quantile regression model for PFOS (in perch; 12 µg/kg ww), PCBs (in eel; 328 µg/kg ww) and benzo(a)pyrene (in mussels: 4.35 µg/kg ww). The lack of a significant regression model for the other compounds indicated an effective threshold value higher than the concentrations measured in the present study. Alternatively, the 95th percentile of concentrations measured in locations with a good ecological quality (MMIF≥0.7), was calculated for all compounds as an additional threshold value. Finally, fish concentrations were standardized for 5% lipid content (or 26% dry weight content for PFOS and Hg). Threshold values for PFOS and benzo(a)pyrene and the 95th percentiles for dioxins and fluoranthene were comparable to the existing standards. For all other compounds, the 95th percentile was higher than the current EQSbiota, while for HBCD, it was lower. These results strongly advise revising and fine-tuning the current EQSbiota, especially for ∑PBDE and HBCD.

Deriving Nickel (Ni(II)) and Chromium (Cr(III)) Based Environmentally Safe Olivine Guidelines for Coastal Enhanced Silicate Weathering.

Enhanced silicate weathering (ESW) by spreading finely ground silicate rock along the coastal zone to remove atmospheric carbon dioxide (CO2) is a proposed climate change mitigation technique. The abundant and fast-dissolving mineral olivine has received the most attention for this application. However, olivine contains nickel (Ni) and chromium (Cr), which may pose a risk to marine biota during a gigaton-scale ESW application. Herein we derive a first guideline for coastal olivine dispersal based on existing marine environmental quality standards (EQS) for Ni and Cr. Results show that benthic biota are at the highest risk when olivine and its associated trace metals are mixed in the surface sediment. Specifically, depending on local sedimentary Ni concentrations, 0.059-1.4 kg of olivine m-2 of seabed could be supplied without posing risks for benthic biota. Accordingly, globally coastal ESW could safely sequester only 0.51-37 Gt of CO2 in the 21st century. On the basis of current EQS, we conclude that adverse environmental impacts from Ni and Cr release could reduce the applicability of olivine in coastal ESW. Our findings call for more in-depth studies on the potential toxicity of olivine toward benthic marine biota, especially in regard to bioavailability and metal mixture toxicity.

A comparative study on the effects of three different metals (Cu, Zn and Cd) at similar toxicity levels in common carp, Cyprinus carpio.

To improve our understanding of underlying toxic mechanisms, it is important to evaluate differences in effects that a variety of metals exert at concentrations representing the same toxic level to the organism. Therefore, the main goal of the present study was to compare the effects of waterborne copper (Cu(II)), zinc (Zn(II)) and cadmium (Cd (II)) on a freshwater fish, the common carp (Cyprinus carpio), at concentrations being 0%, 25%, 50% and 100% of the 96 h LC50 (the concentration which is lethal to 50% of the population in 96 h). All the exposures were performed for a period of 1 week at 20°C. Our results show a rapid increase in the amount of copper and cadmium accumulated in the gills, while zinc only started to increase by the end of the experiment. All three metal ions increased metallothionein gene expression in both gills and liver. However, clear adverse effects were mainly observed for the Cu exposed group. Cu caused a decrease in Na level in gill tissue; it altered the expression of genes involved in ionoregulation such as Na+ /K+ -ATPase and H+ -ATPase as well as the expression of oxidative stress-related genes, such as catalase, glutathione reductase and glutathione S-transferase. Zinc and cadmium exposure did not alter the ion levels in the gills. In addition, no obvious effect of oxidative stress was observed, except for a transient increase in glutathione reductase at the highest cadmium concentration.

Towards harmonization of water quality management: A comparison of chemical drinking water and surface water quality standards around the globe.

Water quality standards (WQS) set the legal definition for safe and desirable water. WQS impose regulatory concentration limits to act as a jurisdiction-specific legislative risk-management tool. Despite its importance in shaping a universal definition of safe, clean water, little information exists with respect to (dis)similarity of chemical WQS worldwide. Therefore, this paper compares chemical WQS for drinking and surface water matrices in eight jurisdictions representing a global geographic distribution: Australia, Brazil, Canada, China, the European Union, the region of Flanders in Belgium, the United States of America, and South Africa. The World Health Organization's list is used as a reference for drinking water standards. Sørensen-Dice indices (SDI) showed little qualitative similarity in the compounds that are regulated in drinking water (median SDI = 40%) and surface water (median SDI = 33%), indicating that the heterogeneity within a matrix is substantial at the level of the standard. Quantitative similarity for matching standards was higher than the qualitative per Kendall correlation (median = 0.73 and 0.58 for drinking water and surface water respectively), yet variance observed within standards remained inexplicably high for organic compounds. Variations in WQS were more pronounced for organic compounds. Most differences cannot be easily explained from a toxicological or risk-based point-of-view. Historical development, ease of measurement, and (toxicological) knowledge gaps on the risk of a vast number of organic compounds are theorized to be the drivers. Therefore, this study argues for a more tailored, risk-based approach in which standards incorporated into water safety plans are dynamically set for compounds that are persistent and could pose a risk for human health and/or aquatic ecosystems. Global variations in WQS should therefore not necessarily be avoided but rather globally harmonized with enough flexibility to ensure a global, up-to-date definition of safe and desirable water everywhere.

Do Aptamers Always Bind? The Need for a Multifaceted Analytical Approach When Demonstrating Binding Affinity between Aptamer and Low Molecular Weight Compounds.

In this manuscript, we compare different analytical methodologies to validate or disprove the binding capabilities of aptamer sequences. This was prompted by the lack of a universally accepted and robust quality control protocol for the characterization of aptamer performances coupled with the observation of independent yet inconsistent data sets in the literature. As an example, we chose three aptamers with a reported affinity in the nanomolar range for ampicillin, a ß-lactam antibiotic, used as biorecognition elements in several detection strategies described in the literature. Application of a well-known colorimetric assay based on aggregation of gold nanoparticles (AuNPs) yielded conflicting results with respect to the original report. Therefore, ampicillin binding was evaluated in solution using isothermal titration calorimetry (ITC), native nano-electrospray ionization mass spectrometry (native nESI-MS), and 1H-nuclear magnetic resonance spectroscopy (1H NMR). By coupling the thermodynamic data obtained with ITC with the structural information on the binding event given by native nESI-MS and 1H NMR we could verify that none of the ampicillin aptamers show any specific binding with their intended target. The effect of AuNPs on the binding event was studied by both ITC and 1H NMR, again without providing positive evidence of ampicillin binding. To validate the performance of our analytical approach, we investigated two well-characterized aptamers for cocaine/quinine (MN4), chosen for its nanomolar range affinity, and l-argininamide (1OLD) to show the versatility of our approach. The results clearly indicate the need for a multifaceted analytical approach, to unequivocally establish the actual detection potential and performance of aptamers aimed at small organic molecules.

The effect of copper on behaviour, memory, and associative learning ability of zebrafish (Danio rerio).

Copper is an essential element in many biological processes, but may exert toxic effects at levels surplus to metabolic requirements. Herein we assess the effect of copper on zebrafish behaviour using two assays, namely the novel tank diving test and a T-maze test with food reward. Novel tank diving tests were conducted on days 0, 4, and 10 of a 10 day Cu exposure (at concentrations of 0.77 µM (25% of the 240 h LC50) and 1.52 µM (50% of the 240 h LC50) to assess the alterations of behavioural responses in repeating novel tank diving assays and the effect of Cu on these patterns. Results demonstrate habituation to novelty, which is an indicator of spatial memory. Copper exposure had no effect on the latency of entry into the upper zones of the tank, nor on the total time spent therein, but did cause a greater number of freezing bouts in comparison to the control group. Additionally, Cu exposure had no effect on the habituation responses of zebrafish. Using the T-maze assay, we tested the effect of prior exposure to Cu for 10 days on subsequent behavioural trainings. The T-maze protocol was based on associative learning, where a visual stimulus (colour) was linked with a natural stimulus (food). Results of the control group showed that zebrafish are able to perform associative learning tasks. Moreover, Cu was found to negatively affect the associative learning capabilities. Specifically, while zebrafish in the control group achieved a significant number of correct choices (leading to food reward) throughout the T-maze training, such a trend was not observed for Cu exposed fish. Thus at the exposure concentrations and exposure times considered herein, Cu has no determinative impact on instinctual behavioural responses of zebrafish in repeated novel tank diving assays but does limit the associative learning capabilities.

Common carp, Cyprinus carpio, prefer branchial ionoregulation at high feeding rates and kidney ionoregulation when food supply is limited: additional effects of cortisol and exercise.

This study aims to examine ionoregulatory parameters during exercise and cortisol elevation in common carp fed different food rations. Fish subjected to two different feeding regimes (0.5 or 3.0% body mass (BM) daily) received no implant or an intraperitoneal cortisol implant (250 mg/kg BM) or sham, and were monitored over a 168-h post-implant (PI) period under resting, low aerobic swimming or exhaustive swimming conditions. Plasma osmolality was maintained at relatively stable levels without much influence of feeding, swimming or cortisol, especially in low feeding groups. Nevertheless, a transient hyponatremia was observed in all low feeding fish implanted with cortisol. The hyponatremia was more pronounced in fish swum to exhaustion but even in this group, Na+ levels returned to control levels as cortisol levels recovered (168 h-PI). Cortisol-implanted fish also had lower plasma Cl- levels, and this loss of plasma Cl- was more prominent in fish fed a high ration during exhaustive swimming (recovered at 168 h-PI). Cortisol stimulated branchial NKA and H+ ATPase activities, especially in high ration fish. In contrast, low ration fish upregulated kidney NKA and H+ ATPase activities when experiencing elevated levels of cortisol. In conclusion, low feeding fish experience an ionoregulatory disturbance in response to cortisol implantation especially when swum to exhaustion in contrast to high feeding fish.

The interplay between chemical speciation and physiology determines the bioaccumulation and toxicity of Cu(II) and Cd(II) to Caenorhabditis elegans.

Using the well-documented model organism Caenorhabditis elegans, a combined analysis of metal speciation in the exposure medium and body burdens of metals (Zn, Cu and Cd) was performed, and factors that are predictive of toxicological endpoints in single metal and mixed metal exposures were identified. Cu, and to a lesser extent Cd, is found to associate with Escherichia coli in the exposure medium (the food source for C. elegans) as evidenced by the observed decrease in both their dissolved and free metal ion concentrations. Together with a critical analysis of literature data, our results suggest that free metal ion concentrations and thus aqueous uptake routes are the best predictor of internal concentrations under all conditions considered, and of metal toxicity in single metal exposures. Additional factors are involved in determining the toxicity of metal mixtures. In general, the eventual adverse effects of metals on biota are expected to be a consequence of the interplay between chemical speciation in the exposure medium, timescale of exposure, exposure route as well as the nature and timescale of the biotic handling pathways.

Optimizing the Use of Zebrafish Feeding Trials for the Safety Evaluation of Genetically Modified Crops.

In Europe, the toxicological safety of genetically modified (GM) crops is routinely evaluated using rodent feeding trials, originally designed for testing oral toxicity of chemical compounds. We aimed to develop and optimize methods for advancing the use of zebrafish feeding trials for the safety evaluation of GM crops, using maize as a case study. In a first step, we evaluated the effect of different maize substitution levels. Our results demonstrate the need for preliminary testing to assess potential feed component-related effects on the overall nutritional balance. Next, since a potential effect of a GM crop should ideally be interpreted relative to the natural response variation (i.e., the range of biological values that is considered normal for a particular endpoint) in order to assess the toxicological relevance, we established natural response variation datasets for various zebrafish endpoints. We applied equivalence testing to calculate threshold equivalence limits (ELs) based on the natural response variation as a method for quantifying the range within which a GM crop and its control are considered equivalent. Finally, our results illustrate that the use of commercial control diets (CCDs) and null segregant (NS) controls (helpful for assessing potential effects of the transformation process) would be valuable additions to GM safety assessment strategies.

Cyclist exposure to black carbon, ultrafine particles and heavy metals: An experimental study along two commuting routes near Antwerp, Belgium.

Urban environments typically exhibit large atmospheric pollution variation, in both space and time. In contrast to traditional monitoring networks suffering from a limited spatial coverage, mobile platforms enable personalized high-resolution monitoring, providing valuable insights into personal atmospheric pollution exposure, and the identification of potential pollution hotspots. This study evaluated personal cyclist exposure to UFPs, BC and heavy metals whilst commuting near Antwerp, Belgium, by performing mobile measurements with wearable black carbon (BC) and ultrafine particle (UFP) instruments. Loaded micro-aethalometer filterstrips were chemically analysed and the inhaled pollutant dose determined from the exhibited heart rate. Considerable spatial pollutant variation was observed along the travelled routes, with distinct contributions from spatial factors (e.g. traffic intersections, urban park and market) and temporary events. On average 300% higher BC, 20% higher UFP and changing elemental concentrations are observed along the road traffic route (RT), when compared to the bicycle highway route (BH). Although the overall background pollution determines a large portion of the experienced personal exposure (in this case 53% for BC and 40% for UFP), cyclists can influence their personal atmospheric pollution exposure, by selecting less exposed commuting routes. Our results, hereby, strengthen the body of evidence in favour of further policy investments in isolated bicycle infrastructure.

A toxicogenomics approach to screen chlorinated flame retardants tris(2-chloroethyl) phosphate and tris(2-chloroisopropyl) phosphate for potential health effects.

Tris(2-chloroethyl) phosphate (TCEP) is a pervasive flame retardant that has been identified as a chemical of concern given its health effects and therefore its use has since been tightly regulated. Tris(2-chloroisopropyl) phosphate (TCIPP), an analogue of TCEP, is believed to be its replacement. However, compared to TCEP, little is known of the toxicological impacts of TCIPP. We used RNA sequencing as unbiased and sensitive tool to identify and compare effects on a transcriptome level of TCEP and TCIPP in the human hepatocellular carcinoma cell line, HepG2. We identified that compared to other flame retardants, TCEP and TCIPP had little cytotoxicity. Treatment with sub-cytotoxic concentrations of the two compounds revealed that both chemicals elicited similar effects; both compounds were found to affect genes involved in immune responses and steroid hormone biosynthesis, while also affecting xenobiotic metabolism pathways in a similar manner. Specifically for effects on immune responses, both compounds were shown to alter the expression of the receptor of the potent and pleiotropic complement component, C5a. Additionally, expression of genes encoding for effector proteins involved in the complement cascade along with other potent inflammatory regulators were found altered in response to TCEP and TCIPP, further emphasizing their potential effects on immune function. Taken together, given that TCIPP elicited similar effects compared to TCEP, and at lower concentrations, the potential health effects of TCIPP need to be further studied for a complete risk assessment of the compound.

Exercise improves growth, alters physiological performance and gene expression in common carp (Cyprinus carpio).

It has been suggested that induced swimming has the potential to improve the growth performance of fish. We tested this hypothesis by measuring growth, metabolic efficiency and physiological capacity of common carp (Cyprinus carpio). Fish were swum at different exercise regimes: 0.0 (control), 1.5 and 2.5 body lengths per second (BL/s) in 1600 L recirculating raceways for 4 weeks. The results showed a significant increase in weight gain, specific growth rate, improved feed conversion efficiency, and a higher hepatosomatic index for 2.5 BL/s exercised fish compared to control. Glycogen, protein and lipid energy stores in hepatic and muscular tissue showed limited differences among experimental groups. Likewise, plasma [Na+], [K+] and [Cl-] remained stable at all swimming regimes. Expression of genes controlling energy metabolism and growth (IGF-I axis, cytochrome oxidase) and stress response (cortisol receptor, heat shock protein 70) revealed clear regulatory roles as the mRNA transcript levels of IGF-I and growth hormone receptors in hepatic tissue were up-regulated in fish exercised for 3-4 weeks at 2.5 BL/s. Oxygen consumption rate and swimming performance (Ucrit) for each experimental group were evaluated in parallel in Blazka-type swim-tunnels (3.9 L) and showed no training effect while prolonged swimming at 1.5 and 2.5 BL/s facilitated ammonia excretion and prevented build-up of plasma ammonia. Overall, these data suggest that sustained exercise at 2.5 BL/s enhanced growth and physiological fitness without compromising energy metabolism or ion-regulation. Our study provides a prospective of implementing exercise as a tool to increase fish production efficiency in commercial aquaculture systems.

Shawn, the Drosophila Homolog of SLC25A39/40, Is a Mitochondrial Carrier That Promotes Neuronal Survival.

Mitochondria play an important role in the regulation of neurotransmission, and mitochondrial impairment is a key event in neurodegeneration. Cells rely on mitochondrial carrier proteins of the SLC25 family to shuttle ions, cofactors, and metabolites necessary for enzymatic reactions. Mutations in these carriers often result in rare but severe pathologies in the brain, and some of the genes, including SLC25A39 and SLC25A40, reside in susceptibility loci of severe forms of epilepsy. However, the role of most of these carriers has not been investigated in neurons in vivo. We identified shawn, the Drosophila homolog of SLC25A39 and SLC25A40, in a genetic screen to identify genes involved in neuronal function. Shawn localizes to mitochondria, and missense mutations result in an accumulation of reactive oxygen species, mitochondrial dysfunction, and neurodegeneration. Shawn regulates metal homeostasis, and we found in shawn mutants increased levels of manganese, calcium, and mitochondrial free iron. Mitochondrial mutants often cannot maintain synaptic transmission under demanding conditions, but shawn mutants do, and they also do not display endocytic defects. In contrast, shawn mutants harbor a significant increase in neurotransmitter release. Our work provides the first functional annotation of these essential mitochondrial carriers in the nervous system, and the results suggest that metal imbalances and mitochondrial dysfunction may contribute to defects in synaptic transmission and neuronal survival. SIGNIFICANCE STATEMENT: We describe for the first time the role of the mitochondrial carrier Shawn/SLC25A39/SLC25A40 in the nervous system. In humans, these genes reside in susceptibility loci for epilepsy, and, in flies, we observe neuronal defects related to mitochondrial dysfunction and metal homeostasis defects. Interestingly, shawn mutants also harbor increased neurotransmitter release and neurodegeneration. Our data suggest a connection between maintaining a correct metal balance and mitochondrial function to regulate neuronal survival and neurotransmitter release.

Systematic Evaluation of Chronic Metal-Mixture Toxicity to Three Species and Implications for Risk Assessment.

Metal contamination generally occurs as mixtures. However, it is yet unresolved how to address metal mixtures in risk assessment. Therefore, using consistent methodologies, we have set up experiments to identify which mixture model applies best at low-level effects, i.e., the independent action (IA) or concentration addition (CA) reference model. The toxicity of metal mixtures (Ni, Zn, Cu, Cd, and Pb) to Daphnia magna, Ceriodaphnia dubia, and Hordeum vulgare was investigated in different waters or soils, totaling 30 different experiments. Some mixtures of different metals, each individually causing <10% inhibition, yielded much larger inhibition (up to 66%) when dosed in combination. In general, IA was most accurate in predicting mixture toxicity, while CA was the most conservative. At low-effect levels important in risk assessments, CA overestimated mixture toxicity to daphnids and H. vulgare, on average, with a factor 1.4 to 3.6. Observed mixture interactions could be related to bioavailability or by competition interactions, either for binding sites of dissolved organic carbon or for biotic ligand sites. Our study suggests that the current metal-by-metal approach in risk evaluations may not be conservative enough for metal mixtures.

Cadmium exposure exerts neurotoxic effects in peacock blennies Salaria pavo.

Cadmium (Cd) is considered as an important factor involved in several neurological disturbances. The aim of this study was to assess the effects of Cd in the brain of peacock blennies Salaria pavo, a species used as a bioindicator of water pollution. A sublethal contamination of 2mg CdCl2 L-1 was performed over periods of 1, 4, 10 and 15 days. Total Cd accumulation was measured in brains and displayed low concentrations throughout the experiment. Partial-length cDNA of different ATP-binding cassette transporters (abcb1, abcc1, abcc2, abcg2 proteins) and acetylcholinesterase (ache) were characterized. mRNA expressions profiles displayed an up-regulation of abcc2 mRNA after 4 days of Cd exposure only while abcg2 mRNA was down-regulated after 10 days only. For AChE, the mRNA transcription and the activity of the enzyme were followed and highlighted that Cd exerted an inhibitory effect on the nervous information transmission. At the histological level, fish exhibited pathological symptoms in the optic tectum and the cerebellum and results showed that the cerebellum was the most affected organ.

The sequencing batch reactor as an excellent configuration to treat wastewater from the petrochemical industry.

In the present study, the influence of a changing feeding pattern from continuous to pulse feeding on the characteristics of activated sludge was investigated with a wastewater from the petrochemical industry from the harbour of Antwerp. Continuous seed sludge, adapted to the industrial wastewater, was used to start up three laboratory-scale sequencing batch reactors. After an adaptation period from the shift to pulse feeding, the effect of an increasing organic loading rate (OLR) and volume exchange ratio (VER) were investigated one after another. Remarkable changes of the specific oxygen uptake rate (sOUR), microscopic structure, sludge volume index (SVI), SVI30/SVI5 ratio, and settling rate were observed during adaptation. sOUR increased two to five times and treatment time decreased 43.9% in 15 days. Stabilization of the SVI occurred after a period of 20 days and improved significantly from 300 mL·g-1 to 80 mL·g-1. Triplication of the OLR and VER had no negative influence on sludge settling and effluent quality. Adaptation time of the microorganisms to a new feeding pattern, OLR and VER was relatively short and sludge characteristics related to aerobic granular sludge were obtained. This study indicates significant potential of the batch activated sludge system for the treatment of this industrial petrochemical wastewater.

(Electro)Sensing of Phenicol Antibiotics-A Review.

The presence of residues from frequent antibiotic use in animal feed can cause serious health risks by contaminating products meant for human consumption such as meat and milk. The present paper gives an overview of the electrochemical methods developed for the detection of phenicol antibiotic residues (chloramphenicol, thiamphenicol, and florfenicol) in different kinds of foodstuffs. Electrochemical sensors based on different biomolecules and nanomaterials are described. The detection limit of various developed methods with their advantages and disadvantages will be highlighted.