The global presence of microplastics in the environment is well documented nowadays. Studies already showed the potential risks that microplastic particles might cause to the ecosystem, while potential human health effects are currently under investigation. As one of the main inputs of these crucial researches, the concentration of microplastics in the environment should be measured precisely, confidently and monitored regularly to determine exposure levels of these pollutants. Some study highlights, that the results are usually inconsistent and uncertain, due to different sampling and sample preparation methods and the lack of quality assurance and quality control of these processes. The need for a standardized methodology is an emerging issue, as this would provide the right tools to establish a global monitoring system of microplastics. Validated sample preparation methods of water (especially freshwater) samples for microplastic analysis are rarely described. To fulfil the gap, this study aims to create and validate a special toolset and the related standard operating procedure for enhanced sample preparation. A newly developed equipment, the Small Volume Glass Separator was designed to easily isolate microplastics from freshwater samples and concentrate the treated sample in a small volume, thus reducing the brine solution use and the sample transfer steps. These features enable better prevention of contamination and making sample preparation easy, fast and cost-effective. The Small Volume Glass Separator and the related standard operation procedure was validated on model freshwater and wastewater samples with the use of fluorescently tagged microplastics and environmentally relevant microplastics (fragments, fibres). Recoveries were measured with optical microscopy under UV light and with near-infrared spectroscopy/microscopy. Recovery tests with fluorescently tagged microspheres showed that average recovery with the Small Volume Glass Separator is 12-39% higher than that of a widespread sample preparation method. This procedure was also able to recover on average 64%±29% of all the environmentally relevant particles during the validation process. Results show that size and density have a great influence on potential particle loss. Recovery of smaller particles are less with both methods than that of the larger particles, but Small Volume Glass Separator yielded significantly higher recovery for more dense particles. The results of this study help to better understand particle loss during sample preparation and thus contribute to the establishment of standardised microplastic analysis processes.

Xenobiotics never appear as single, isolated substances in the environment but instead as multi-component mixtures. However, our understanding of the ecotoxicology of mixtures is far from sufficient. In this study, three active pharmaceutical ingredients (carbamazepine, diclofenac, and ibuprofen) and three pesticides (S-metolachlor, terbuthylazine, and tebuconazole) from the most frequently detected emerging micropollutants were examined for their acute cytotoxicity, both individually and in combination, by bioluminescence inhibition in Aliivibrio fischeri (NRRL B-11177). Synergy, additive effects, and antagonism on cytotoxicity were determined using the combination index (CI) method. Additionally, PERMANOVA was performed to reveal the roles of these chemicals in binary, ternary, quaternary, quinary, and senary mixtures influencing the joint effects. Statistical analysis revealed a synergistic effect of diclofenac and carbamazepine, both individually and in combination within the mixtures. Diclofenac also exhibited synergy with S-metolachlor and when mixed with ibuprofen and S-metolachlor. S-metolachlor, whether alone or paired with ibuprofen or diclofenac, increased the toxicity at lower effective concentrations in the mixtures. Non-toxic terbuthylazine showed great toxicity-enhancing ability, especially at low concentrations. Several combinations displayed synergistic effects at environmentally relevant concentrations. The application of PERMANOVA was proven to be unique and successful in determining the roles of compounds in synergistic, additive, and antagonistic effects in mixtures at different effective concentrations.

In the field of microplastic (MP) research in the environment, a significant amount of the currently reported results is uncertain because of the inappropriate methods of sampling, detection and quantification of MPs. Fortunately, many research groups are aware of these challenges, but validated methods, which are the prerequisite of standardized measurements, are scarce. Recovery tests are especially rare in the field of MP sampling. The aim of our research was to take a step forward and collect data on cascade filtration recoveries by modeling different turbulance conditions and sampling depth applying environmentally relevant MP concentrations while obtaining large sample volumes. As reference materials, different polymer types (polyethylene - PE; polypropylene - PP; poly[ethylene terephthalate] - PET; poly[vinyl chloride] - PVC; polyamide - PA) and shapes (sphere, fragment, fiber) were used, and for detection near-infrared spectroscopy/microscopy was applied. The developed method provides information not only on system based MP losses, but on sampling efficiency in a model environment as well. Based on the results, the highest recovery rate of all polymers was 31.4% on average, sampled from the water surface during continuous stirring. In these conditions, 92.4% of the PE spheres and 31.9% of the PE fragments were recovered. This indicates, particles reported in environmental monitoring studies might be less than the real environmental concentration. We can conclude, that surface sampling is more efficient than sampling in a deeper layer of the water column. Our research revealed, that the widespread application of microspheres as reference materials might lead to too optimistic recovery values. The application of reference particles (fragments, fibers) with higher environmental relevance shows much lower recovery rates. Our results highlight, that validating the efficiency of the whole sampling process from the environment is more important than measuring only the filtration device's recovery. This study helps us to better understand the relationship and the possible gaps between the reported MP results and the real-life concentrations in the environment.

Balaton is the largest shallow lake in Central Europe. It is one of the few lakes where eutrophication processes have been successfully reversed. The creation of a wetland area on the lower part of the main inflow river played a major role in the re-oligotrophication processes. After several decades of operation and multiple transformations, an attempt was made to explore the microbial community of the water reservoir and its relationship with algal groups and environmental parameters. In the main inflow river, floods had the greatest effect on the microbial community composition, while in the open water areas of the wetland system, the algae production that develops due to external nutrient load was the main driver of the bacterial community. In the high-macrophyte-covered areas, the decomposition processes of the dying algae biomass were the most decisive. Finally, in the large open water areas of Lake Balaton, the external and internal nutrient loads together determined the algal production and thus the bacterial community composition.

The concentration of microplastics (MPs) in two important Hungarian freshwater habitats was determined in the size range of 50 μm–1 mm. Lake Balaton (LB) is the largest shallow lake in Central Europe, with a significant role in recreation and tourism. Its main inflow, the Zala River, enters the lake through an artificially constructed wetland, the Kis-Balaton Water Protection System and its catchment area (KB), which helps preserve the water quality of the lake. From these two areas, 15 samples were taken with an in situ filtration sampling method. After preparation, the samples were analyzed automatically by FT-IR microscopy. All samples, from both areas, contained MPs; the dominant microplastic (MP) shape was the fragment, while the most frequently polymer types were polyethylene, polypropylene and alkyd. Small MPs were dominant in both areas; around 90% of the MPs were smaller than 500 μm. On average, LB contained more MPs (21.0 ± 12.5 MPs/m³) compared to the KB, which presented an average concentration of MPs of 7.8 ± 5.9 MPs/m³. In the examined areas, two potential MP sources were determined, i.e., treated wastewater and road traffic. The importance of tourism should also be further investigated.

In this study, the disrupting effects of glyphosate (GLY), aminomethylphosphonic acid (AMPA), and three glyphosate-based herbicides (GBHs) on vitellogenesis in a non-concentration-dependent manner are reported for the first time in 120 h of acute exposure of zebrafish at environmentally relevant concentrations. GBHs are commonly used worldwide in weed control management. Due to their extensive application, they frequently occur in aquatic ecosystems and may affect various organisms. The active substance GLY and its major by-product, AMPA, are the most thoroughly studied chemicals; however, the adverse effects of the complex formulas of GBHs with diverse and unknown content of co-formulants are still not sufficiently researched. This study focused on the embryotoxicity, sublethal malformations, and estrogenic potency of GLY, AMPA, and four commonly used GBHs on zebrafish embryos using a wild type and an estrogen-sensitive, transgenic zebrafish line (Tg(vtg1:mCherry)). After 120 h of exposition, AMPA did not cause acute toxicity, while the LC₅₀ of GLY was 160 mg/L. The GBHs were more toxic with LC₅₀ values ranging from 31 to 111 GLY active equivalent (a.e.) mg/L. Exposure to 0.35-2.8 mg/L GBHs led to sublethal abnormalities: typical symptoms were structural deformation of the lower jaw and anomalies in the olfactory region. Deformity rates were 10-30% in the treated groups. In vivo, fluorescently expressed vtg1 mCherry protein in embryonic liver was detected by a non-invasive microscopic method indicating estrogenic action through vitellogenin production by GLY, AMPA, and GBHs. To confirm the in vivo findings, RT-qPCR method was performed to determine the levels of the estrogenicity-related vtg1 mRNA. After 120 h of exposure to GLY, AMPA, and three GBHs at a concentration of 0.35 mg/L, the expression of vtg1 gene was significantly up-regulated. Our results highlight the risk that short-term GLY and GBH exposure can cause developmental malformations and disrupt the hormonal balance in zebrafish embryos.