Hydrodynamic cavitation-enhanced activation of sodium percarbonate for estrogen removal.

The present paper investigated the potential of hydrodynamic cavitation (HC) as an effective tool for activating sodium percarbonate (SPC). The method's efficiency was demonstrated by effectively removing estrogens, which are pollutants that have adverse impacts on aquatic ecosystems. The effects of the SPC concentration, temperature of solution, and cavitation time were evaluated. After SPC/HC treatment, the removal of estrogens was monitored by liquid chromatography-tandem mass spectrometry (LC -MS/MS). Already after 4 s of treatment and 24 h of reaction time, more than 97% of estrogens (initial concentration of 300 ng/L) were removed. The effect of post-treatment time is not considered in several papers, even though it seems to be crucial and is discussed here. The results were supported by the values of degradation rate constants, which fit the pseudo-first-order kinetic model. We also verified that HC alone was not effective for estrogen removal under the selected conditions. The sustainability of the SPC/HC system was evaluated based on electric energy per order calculation. The combination of SPC and HC is a promising approach for rapidly degrading micropollutants such as estrogenic compounds without the need for additional technological steps, such as pH or temperature adjustment.

High-pressure jet-induced hydrodynamic cavitation as a pre-treatment step for avoiding cyanobacterial contamination during water purification.

Due to specific physical properties, hydrodynamic cavitation (HC) is assigned to the powerful technologies for treating the biotic contamination in water including cyanobacteria. Contaminated water stream (CWS) can be cavitated directly by passing through some HC device, or indirectly when high-pressure jet stream (HPJS) is directed against its flow. Relatively small HPJS stream can thus treat a big volume of CWS in a short time or even work in continuous mode. Cyanobacteria floating in the CWS are forced to flow through the mixing cavitation zone. Within 2 h after single HC treatment, cyanobacterial cell suspensions showed disintegration of larger colonies and enhanced biomass sedimentation. Additional pre-treatment of CWS with low amounts of hydrogen peroxide (H2O2; 33, 66 and 99 µmol/L) enhanced the effect of HC and led to further inhibition of cyanobacterial photosynthesis (maximum quantum yield of photosystem II decreased by up to 60%). The number of cyanobacterial cells in the treated CWS decreased continuously over 48 and 72 h, though some cells remained alive and were able to recover photosynthetic activity. The technique proposed (direction of a HPJS against a CWS and pre-treatment with low H2O2 concentrations) provides (i) effective removal of cells from the water column, and (ii) reduced contamination by organic compounds released from the cells (especially cyanotoxins) as the cell membranes are not destroyed and the cells remain alive. This process shows potential as an effective pre-treatment step in water purification processes related to cyanobacterial contamination.

The effect of silver nanoparticles and silver ions on zebrafish embryos (Danio rerio).

OBJECTIVES: The aim of this study was to establish and evaluate the mortality rate, hatching rate and observe the presence of sublethal changes in zebrafish embryos after exposure to silver ions and nanoparticles. METHODS: Tests were conducted on newly fertilized zebrafish embryos, according to the modified OECD guideline 236, using a semistatic method and 96 hour incubation time. Silver nitrate and two different silver nanoparticles, stabilized with 0.01% solution of maltose and gelatine in the first case, and stabilized with polyvinylpyrrolidone, in the latter, were tested. RESULTS: Significant differences in toxicity of tested substances were recorded. The value of 96hLC50 for silver nitrate was 58.44 µg/L. The value of 96hLC50, calculated for silver nanoparticles stabilized with 0.01% solution of maltose and gelatine, was nearly 100 times higher, 4.31 mg/L. The value 96hLC50 for silver nanoparticles stabilized with polyvinylpyrrolidone exceeded 100mg/L, occurrence of sublethal effects caused by silver nanoparticles stabilized with polyvinylpyrrolidone was insignificant in most of the exposition groups, but only in this substance caused decreased hatching rate. CONCLUSION: Properties of different silver nanoparticles play an important role in levels of their toxicity and predominant mechanisms of action. In general, silver nanoparticles are less toxic for Danio rerio embryos than silver ions.

High-valent iron (Fe(VI), Fe(V), and Fe(IV)) species in water: characterization and oxidative transformation of estrogenic hormones.

This paper presents solid state synthesis and characterization of tetra-oxy iron(iv) and iron(v) species in their salt forms (Na4FeO4-Fe(IV) and K3FeO4-Fe(V)). Stability of the synthesized salts, commonly called ferrates, in water was determined by applying the (57)Fe Mössbauer spectroscopy technique. Within 2 s in water, Fe(IV) converted into Fe(III) while Fe(V) transformed into Fe(VI) and Fe(III) at pH = 8.2. Comparatively, Fe(VI) (bought as K2FeO4) remained stable in aqueous solution during the short time period. The oxidative removal efficiency of the high-valent iron species was then tested against five environmentally important estrogenic hormones (estron (E1), 17-ß-estradiol (E2), estriol (E3), 17-α-ethinylestradiol (EE2), and diethylstibestrol (DES)) in effluent water of a wastewater treatment plant. Three dosages of iron species (1, 10, and 100 mg L(-1)) were applied to the effluent water. An increase in the concentration of dosages enhanced the removal of estrogens. Both Fe(V) and Fe(VI) were effective in degrading estrogens, but Fe(IV) showed limited oxidation capacity to transform estrogens. The oxidized products of the estrogens were analyzed using Raman spectroscopy and high-performance liquid chromatography-mass spectrometry (HPLC-MS) techniques. Results demonstrated the transformation of estrogens into low molecular weight oxygenated compounds such as quinone-like and opened-aromatic ring species. A detailed study on E1 by using excess Fe(VI) showed the mineralization of the parent compound. The results demonstrate great potential of high-valent iron species in the degradation of endocrine disruptor chemicals like estrogens with several superior aspects including fast reactions, complete degradation and/or formation of benign organic species, and environmentally-acceptable iron oxide by-products.

Oxidation of microcystin-LR by ferrate(VI): kinetics, degradation pathways, and toxicity assessments.

The presence of the potent cyanotoxin, microcystin-LR (MC-LR), in drinking water sources poses a serious risk to public health. The kinetics of the reactivity of ferrate(VI) (Fe(VI)O4(2-), Fe(VI)) with MC-LR and model compounds (sorbic acid, sorbic alcohol, and glycine anhydride) are reported over a range of solution pH. The degradation of MC-LR followed second-order kinetics with the bimolecular rate constant (kMCLR+Fe(VI)) decreasing from 1.3 ± 0.1 × 10(2) M(-1) s(-1) at pH 7.5 to 8.1 ± 0.08 M(-1) s(-1) at pH 10.0. The specific rate constants for the individual ferrate species were determined and compared with a number of common chemical oxidants employed for water treatment. Detailed product studies using liquid chromatography-mass spectrometry/mass spectrometry (LC-MS/MS) indicated the oxidized products (OPs) were primarily the result of hydroxylation of the aromatic ring, double bond of the methyldehydroalanine (Mdha) amino acid residue, and diene functionality. Products studies also indicate fragmentation of the cyclic MC-LR structure occurs under the reaction conditions. The analysis of protein phosphatase (PP1) activity suggested that the degradation byproducts of MC-LR did not possess significant biological toxicity. Fe(VI) was effective for the degradation MC-LR in water containing carbonate ions and fulvic acid (FA) and in lake water samples, but higher Fe(VI) dosages would be needed to completely remove MC-LR in lake water compared to deionized water.

A fast and reliable LC-MS-MS method for the quantification of saxitoxin in blood plasma samples.

Saxitoxins (STXs) are potent neurotoxins produced by marine dinoflagellates or freshwater cyanobacteria known to cause acute and eventually fatal human intoxications, which are classified as paralytic shellfish poisonings (PSPs). Rapid analysis of STXs in blood plasma can be used for a timely diagnosis and confirmation of PSPs. We developed a fast and simple method of STX extraction based on plasma sample acidification and precipitation by acetonitrile, followed by quantification using liquid chromatography-tandem mass spectrometry (LC-MS-MS). Our approach provides the results ≤30 min, with a limit of detection of 2.8 ng/mL and a lower limit of quantification of 5.0 ng/mL. Within-run and between-run precision experiments showed good reproducibility with ≤15% values. Standard curves for calibration were linear with correlation coefficients ≥0.98 across the assay calibration range (5-200 ng/mL). In an interlaboratory analytical exercise, the method was found to be 100% accurate in determining the presence or absence of STX in human plasma specimens, with recovery values of 86-99%. This simple method for STX determination in animal or human plasma can quickly and reliably diagnose STX exposures and confirm suspected PSP cases to facilitate patient treatment or expedite necessary public health or security actions.

Potential toxicity of Schisandra chinensis to water environment: acute toxicity tests with water crustaceans.

Fruits of Schisandra chinensis, an East Asian liana plant, are currently more and more used to produce nutrient supplements that positively affect human health due to the content of various secondary metabolites. On the other hand, these substances because of their bioactivity can cause possible allelopathic or toxic effects concerning other organisms (algae, plants, animals). But the ecotoxicological properties of S. chinensis outside its area of origin have yet to be sufficiently verified. Two crustaceans, Daphnia magna and Thamnocephalus platyurus, were selected as model aquatic organisms to test the potential impact of S. chinensis active compounds on the aquatic environment. Crude water extract from S. chinensis fruits, simulating the natural leakage of active substances in water, was tested in treatments from 0.0045 to 45 mg/L (according to the content of schisandrin as the dominating lignan). Effective concentration (EC50) causing 50% lethal effect for D. magna was established to 0.0448 mg/L after 24 h and 0.0152 mg/L after 48 h. EC50 for T. platyurus reached 0.4572 mg/L after 24 h, i.e. more than ten times higher than for D. magna. This study showed that the potential environmentally relevant concentrations of S. chinensis bioactive compounds could represent a severe risk to aquatic ecosystems.

Bioactive compounds from Schisandra chinensis - Risk for aquatic plants?

Schisandra chinensis is a potential plant for production of nutrient supplements due to adaptogens content. The dominant bioactive substance, lignan schisandrin, has positive effects on human health, but it can cause possible allelopathic effects in relation to other plants. S. chinensis is not native to European ecosystems, and its ecotoxicological properties have not been verified yet. Lemna minor was selected as a model aquatic plant to test its potential impact on the aquatic environment. Crude water extract from S. chinensis fruits, simulating the natural soaking of active substances in a surface water body, was used in treatments from 0.045 to 45 mg/L (according to the content of schisandrin as the dominating lignan). During seven days of cultivation, the growth (number of plants, leaf area, fresh weight) and photosynthetic activity of L. minor fronds were assessed. In low treatments (0.045 and 0.09 mg/L), the extract of S. chinensis did not cause any changes in duckweed growth parameters or photosynthetic performance. Higher treatments (0.45 and 0.9 mg/L) caused significant limitations in plants' number, total leaf area, and fresh weight. The photosynthetic parameters (basal chlorophyll fluorescence, quantum yields) were affected only by 0.9 mg/L. The highest treatment, 45 mg/L, exhibited extreme toxicity to duckweed plants causing their death during the first five days of cultivation. Schisandrin and other bioactive substances extractable from S. chinensis fruits can negatively impact water biota in the case of massive contamination of surface water.

Multimodal action and selective toxicity of zerovalent iron nanoparticles against cyanobacteria.

Cyanobacteria pose a serious threat to water resources around the world. This is compounded by the fact that they are extremely resilient, having evolved numerous protective mechanisms to ensure their dominant position in their ecosystem. We show that treatment with nanoparticles of zerovalent iron (nZVI) is an effective and environmentally benign method for destroying and preventing the formation of cyanobacterial water blooms. The nanoparticles have multiple modes of action, including the removal of bioavailable phosphorus, the destruction of cyanobacterial cells, and the immobilization of microcystins, preventing their release into the water column. Ecotoxicological experiments showed that nZVI is a highly selective agent, having an EC(50) of 50 mg/L against cyanobacteria; this is 20-100 times lower than its EC(50) for algae, daphnids, water plants, and fishes. The primary product of nZVI treatment is nontoxic and highly aggregated Fe(OH)(3), which promotes flocculation and gradual settling of the decomposed cyanobacterial biomass.

Graphene oxide interaction with Lemna minor: Root barrier strong enough to prevent nanoblade-morphology-induced toxicity.

The production of graphene oxide (GO) along with its applications in various aquatic environments is vastly increasing thanks to its rapidly expanding range of new GO-based environmental technologies. Therefore, the fate of GO in aquatic environments is an important issue, as it could become an environmental challenge if its potential toxic mechanism is not addressed properly. Number of studies reporting the toxicity of GO to various aquatic organisms is still increasing. However, research data on the possible toxic mechanism of GO towards aquatic plants have yet to be collected, especially regarding GO's surface chemistry. Here, we studied the interaction of three differently oxidized GO systems with model aquatic plant Lemna minor. We found that although none of the three GOs caused lethal phytotoxicity to Lemna after 7 days, the mechanism of action was dependent on the GO's surface oxidation. Based on the amount of functional surface groups, the GO was able to directly interact with the Lemna's root through its edges. However, in this case in contrast to algae and crustaceans, the interaction did not lead to a mechanical damage. Therefore, our results showed that GO is not hazardous to Lemna minor even at very high concentrations (up to 25 mg/L), because the root barrier proved to be strong enough to prevent GO's penetration and its consequent toxicity.

Effects of microcystin and complex cyanobacterial samples on the growth and oxidative stress parameters in green alga Pseudokirchneriella subcapitata and comparison with the model oxidative stressor--herbicide paraquat.

Oxidative stress is one of the biochemical mechanisms involved in toxicity of cyanobacterial toxins microcystins (MC), but its role in the effects of complex water blooms is elusive. The aim of this study was to investigate effects of pure MCs and different complex mixtures of cyanobacterial metabolites on the growth and biochemical markers of oxidative stress and detoxification in green alga Pseudokirchneriella subcapitata. Pure MCs at high concentrations (300 µg/L) had no effects on the growth of P. subcapitata (up to 10 day exposures) but stimulated activity of glutathione reductase (GR) after short 3 and 24 h exposures. Other biomarkers (levels of glutathione, GSH, and activities of glutathione-S-transferase, GST, and glutathione peroxidase, GPx) were not affected by pure MCs). Crude extract of the laboratory culture of cyanobacteria Microcystis aeruginosa (containing 300 µg/L of MCs) had no effects on algal growth or any of the biomarkers. Weak growth stimulations after 4-7 days were observed after exposures to the growth-spent medium of the M. aeruginosa culture, which also inhibited activities of GST after prolonged exposures. Other investigated parameters (reduced GSH and activity of GPx) were not affected by any of the cyanobacterial samples. The results were compared with effects of model oxidative stressor herbicide paraquat, which exhibited variable effects on both algal growth and biomarkers (decrease in reduced GSH, stimulations of GR). Taken together, although pure MCs induce oxidative stress in green alga, the effects of cyanobacterial mixtures, which are more relevant to the natural situation, are more complex and they differ from the pure toxin. High variability in the biochemical responses to the oxidative stress makes the interpretation of results complicated, which limits the use of these biomarkers as early warnings of toxicity under natural conditions.

Oxidation of antibiotics by ferrate(VI) in water: Evaluation of their removal efficiency and toxicity changes.

Antibiotics in water and wastewater have been determined extensively. The treatment of antibiotics in water needs evaluation of possible harmful effects on aquatic ecosystems and human health. This paper presents the toxicity evaluation of antibiotics after their treatment with ferrate (VI) (FeVIO42-, Fe(VI)) in water. The antibiotics (sulfamethoxazole (SMX), erythromycin (ERY), ofloxacin (OFL), ciprofloxacin (CIP), tetracycline (TET), oxytetracycline (OXY), and trimethoprim (TMP)) were treated at pH 8.0 by applying two concentrations of Fe(VI) to have molar ratios of 5:1 and 10:1 ([Fe(VI)]:[antibiotic]). Under the studied conditions, incomplete removal of antibiotics was observed, suggesting that the treated solutions contained parent antibiotics and their transformation products. The toxicity of antibiotics without Fe(VI) treatment was tested against freshwater green alga Raphidocelis subcapitata and cyanobacterium Synechococcus elongatus, which were determined to be generally sensitive to antibiotics, with EC50 < 1.0 mg/L. The toxicity of Fe(VI) treated solution was tested against R. subcapitata. Results found no toxicity for the treated solutions of OFL, CIP, and OXY. However, SMX, ERY, and TET remained toxic after Fe(VI) treatment (i.e., more than 75% growth inhibition of R. subcapitata). Results demonstrated that R. subcapitata may be applied to test the toxicity of antibiotics after oxidative treatments.

Evaluation of the novel passive sampler for cyanobacterial toxins microcystins under various conditions including field sampling.

In the present study, we have evaluated the effectiveness of a passive sampler for polar organic chemicals to accumulate a group of widespread and hazardous tumor-promoting toxins produced in cyanobacterial water blooms-microcystins (MC). The previously optimized configuration of the sampler based on polycarbonate membrane and Oasis HLB sorbent (2.75 mg/cm(2)) was validated under various exposure scenarios in laboratory and field. Calibration of the passive sampler conducted under variable conditions and concentrations of MC revealed linearity of the sampling up to 4 weeks. The sampling rates of microcystins for two different exposure scenarios were derived (e.g., MC-LR: R (s) = 0.017 L/day under static and 0.087 L/d under turbulent conditions). R (s) values were further used for calculations of time-weighted average concentrations in natural water. Improved sensitivity and selectivity of the in-house-made sampler was observed in comparison with the commercially available Polar Organic Compound Integrative Sampler (POCIS). Comparisons of grab and passive sampling methods were performed during cyanobacterial water bloom season in the Brno reservoir, Czech Republic in 2008. Data obtained by passive sampling provided a more relevant picture of the situation and enabled better assessment of potential risks. The present study demonstrated that the modification of POCIS is suitable for monitoring of occurrence and retrospective estimations of microcystin water concentrations, especially with respect to the control of drinking water quality.

Degradation of natural toxins by phthalocyanines--example of cyanobacterial toxin, microcystin.

Phthalocyanines (Pcs) are promising photosensitizers for use in various branches of science and industry. In the presence of visible light and diatomic oxygen, phthalocyanines can react to produce singlet oxygen, a member of reactive oxygen species able to damage different molecules and tissues. The aim of this study was to investigate the ability of phthalocyanines to degrade natural toxins in the presence of visible light. As the representative of hardly degradable toxins, a group of cyanobacterial peptide toxins--microcystin-LR--was chosen for this study. According to our results, phthalocyanines are able to degrade 61.5% of microcystins within a 48-hour incubation (38% of microcystins was degraded after 24 h and 24% after 12 h of incubation). Although other oxidants like hydrogen peroxide or ozone are able to degrade microcystins within several hours, we assume that by optimizing the spectrum emitted by light source and by changing the absorption characteristics of Pcs, microcystins degradation by phthalocyanines could be more effective in the near future.

The environmental fate of graphene oxide in aquatic environment-Complete mitigation of its acute toxicity to planktonic and benthic crustaceans by algae.

Graphene oxide (GO) as the most studied hydrophilic graphene derivative can be deployed in a broad spectrum of environmental technologies opening the issue of its ecotoxicity. Nevertheless, the information about its behavior in complex aquatic environment is still not sufficient. Here, we studied the interaction of three differently oxidized GO systems with planktonic and benthic crustaceans. By standard toxicity tests, we observed the importance of feeding strategy as well as the surface oxidation of GO with respect to GO's ecotoxicity. However, to gain a clearer insight into GO's environmental fate, we introduced a pre-treatment with algae as the most common source of food for crustaceans. Such an adjustment mimicking the conditions in real aquatic ecosystems resulted in complete mitigation of acute toxicity of GOs to all organisms and, more importantly, to the eradication of oxidative stress caused by GOs. We argue, that the pre-exposition of food is a crucial factor in GO's overall environmental fate, even though this fact has been completely neglected in recent studies. These experiments proved that GO is not a hazardous material in complex aquatic environments because its acute toxicity can be successfully mitigated through the interaction with algae even at very high concentrations (25 mg/L).

Interspecies interactions can enhance Pseudomonas aeruginosa tolerance to surfaces functionalized with silver nanoparticles.

Development of anti-fouling surfaces is a major challenge in materials research. Microorganisms growing as biofilms have enhanced tolerance to antimicrobial strategies including antibiotics and antiseptics complicating the design of anti-fouling surfaces. Silver nanoparticles (AgNPs) are a promising antimicrobial technology with broad spectrum efficacy with a reduced likelihood of microorganisms developing resistance to the technology. This study tested the efficacy of new immobilized AgNP-modified surface technology against three common opportunistic pathogens grown either as monocultures or as cocultures. The presented study fills a gap in the literature by quantifying the efficacy of immobilized AgNP particles against multispecies biofilms. Polyethylene (PE) surfaces functionalized with the AgNPs were highly effective against Pseudomonas aeruginosa biofilms reducing viable cell counts by 99.8 % as compared to controls. However, the efficacy of the AgNP-modified PE surface was compromised when P. aeruginosa was cocultured with Candida albicans. Interspecies interactions can strongly influence the efficacy of anti-fouling AgNP coatings highlighting the need to test surfaces not only against biofilm phenotypes but under conditions representative of applications including the presence of multispecies consortia.

Occurrence and toxicity of antibiotics in the aquatic environment: A review.

In recent years, antibiotics have been used for human and animal disease treatment, growth promotion, and prophylaxis, and their consumption is rising worldwide. Antibiotics are often not fully metabolized by the body and are released into the aquatic environment, where they may have negative effects on the non-target species. This review examines the recent researches on eight representative antibiotics (erythromycin, trimethoprim, sulfamethoxazole, tetracycline, oxytetracycline, ofloxacin, ciprofloxacin, and amoxicillin). A detailed overview of their concentrations in surface waters, groundwater, and effluents is provided, supported by recent global human consumption and veterinary use data. Furthermore, we review the ecotoxicity of these antibiotics towards different groups of organisms, and assessment of the environmental risks to aquatic organisms. This review discusses and compares the suitability of currently used ecotoxicological bioassays, and identifies the knowledge gaps and future challenges. The risk data indicate that selected antibiotics may pose a threat to aquatic environments. Cyanobacteria were the most sensitive organisms when using standard ecotoxicological bioassays. Further studies on their chronic effects to aquatic organisms and the toxicity of antibiotic mixtures are necessary to fully understand the hazards these antibiotics present.

The first occurrence of the cyanobacterial alkaloid toxin cylindrospermopsin in the Czech Republic as determined by immunochemical and LC/MS methods.

Cylindrospermopsin (CYN) is a newly emerging carcinogenic alkaloid originally identified in tropical cyanobacteria Cylindrospermopsis raciborskii. Some recent studies reported production of this toxin also by other cyanobacteria in European countries. Here we report comparison of the immunochemical ELISA determination with the liquid chromatography/mass spectrometry (LC/MS) method for CYN analyses in the samples from the Czech Republic, Central Europe. We have analysed 56 samples of raw lake waters collected from 32 localities. CYN was found at 3 localities with Aphanizomenon sp. sub-dominated water blooms. Results of the ELISA and LC/MS showed good qualitative agreement. However, concentrations determined by ELISA (0.4-4 microg/L) were systematically higher than concentrations determined by LC/MS (0.01-0.3 microg/L). Differences between methods could be attributed to matrix effects (both in ELISA and LC/MS) or ELISA cross-reactivity with other unidentified derivatives of CYN. Our study demonstrates for the first time occurrence of CYN in the Central Europe. With respect to its suspected carcinogenicity, further research on distribution, concentrations and risks of this cyanobacterial toxin is needed.

Application of passive sampling for sensitive time-integrative monitoring of cyanobacterial toxins microcystins in drinking water treatment plants.

Calibrated adsorption-based passive samplers were used for time-integrative monitoring of microcystins (MCs) in three full-scale drinking water treatment plants (DWTPs) in the Czech Republic during two vegetation seasons (Jun-Nov), in parallel with traditional discrete sampling. MCs were detected in epilimnetic water samples at concentrations up to 14 µg/L, but their levels in raw water in DWTPs were below 1 µg/L WHO guideline value for drinking water. Conventional treatment technologies (coagulation/filtration) eliminated cyanobacteria and intracellular toxins but had a limited removal efficiency for extracellular toxins. MCs were regularly detected in final treated water, especially in DWTPs equipped only with the conventional treatment, but their concentrations were below the quantitation limit of discrete sampling (<25 ng/L). Passive samplers in combination with LC-MS/MS analysis provided excellent sensitivity allowing to detect time-weighted average (TWA) concentrations of MCs as low as 20-200 pg/L after 14-d deployment. Median MC TWA concentrations in the treated water from the individual DWTPs were 1-12 ng/L, and most likely did not present significant health risks. Passive samplers well reflected spatiotemporal variations of MCs, actual concentrations of extracellular toxins, MC removal efficiency in DWTPs, and toxin concentrations in the treated water. Passive sampling can be effectively used for assessment and management of MC health risks during DWTP operation.

A novel approach for monitoring of cyanobacterial toxins: development and evaluation of the passive sampler for microcystins.

We have investigated the ability of an integrative sampler for polar organic chemicals to sequestrate a group of common and highly hazardous cyanobacterial toxins-microcystins. In a pilot experiment, commercially available passive samplers were shown to effectively accumulate microcystins after 7 days' exposure in the field. To find the most efficient configuration for sequestration of microcystins, four different porous membranes (polycarbonate, polyester, polyethersulfone and nylon) and two sorbents (Oasis HLB and Bondesil-LMS) were evaluated in the laboratory experiments, where samplers of different configuration were exposed to microcystins (microcystin-RR and microcystin-LR) for 14 days under steady conditions. We observed differences in sampling rates and amounts of accumulated microcystins depending on the sampler configurations. The samplers constructed with the polycarbonate membrane and Oasis HLB sorbent (2.75 mg/cm2) provided the highest sampling rates (0.022 L/day for microcystin-RR and 0.017 L/day for microcystin-LR). To the best of our knowledge, the present study is the first reporting application of passive samplers for microcystins, and our results demonstrate the suitability of this tool for monitoring cyanotoxins in water.