Vojtech Antoš

The use of biological indicators of environmental quality is an alternative method of monitoring ecosystem pollution. Various groups of contaminants, including organic ones, can be measured in environmental samples. Polycyclic aromatic hydrocarbons (PAHs) have not yet been determined by the moss bag technique. This technique uses several moss species simultaneously in urban areas to select the best biomonitoring of these compounds, which are dangerous to humans and the environment. In this research, a gas chromatography coupled with mass spectrometry was used for the determination of selected PAHs in three species of mosses: Pleurozium schreberi, Sphagnum fallax and Dicranum polysetum (active biomonitoring) and for comparison using an air filter reference method for atmospheric aerosol monitoring. The chlorophyll fluorescence of photosystem II (PSII) was also measured to assess changes in moss viability during the study. As a result of the study, the selective accumulation of selected PAHs by mosses was found, with Pleurozium schreberi being the best bioindicator—9 out of 13 PAHs compounds were determined in this species. The photosynthetic yield of photosystem (II) decreased by 81% during the exposure time. The relationship between PAHs concentrations in mosses and the total suspended particles (TSP) on the filter indicated the possibility of using this bioindicator to trace PAHs in urban areas and to apply the moss bag technique as a method supporting classical instrumental air monitoring.

A stall of cis-1,2-DCE and vinyl chloride (VC) is frequently observed during bioremediation of groundwater chloroethenes via reductive dechlorination. These chloroethenes may be oxidised by aerobic methanotrophs or ethenotrophs co-metabolically and/or metabolically. We assessed the potential for such oxidation at 12 sites (49 groundwater samples) using hydrochemical and molecular biological tools. Both ethenotroph (etnC and etnE) and methanotroph (mmoX and pmoA) functional genes were identified in 90% of samples, while reductive dehalogenase functional genes (vcrA and bvcA) were identified in 82%. All functional genes were simultaneously detected in 78% of samples, in actively biostimulated sites in 88% of samples. Correlation analysis revealed that cis-1,2-DCE concentration was positively correlated with vcrA, etnC and etnE, while VC concentration was correlated with etnC, etnE, vcrA and bvcA. However, feature selection based on random forest classification indicated a significant relationship for the vcrA in relation to cis-1,2-DCE, and vcrA, bvcA and etnE for VC and no prove of relationship between cis-1,2-DCE or VC and the methanotroph functional genes. Analysis of hydrochemical parameters indicated that aerobic oxidation of chloroethenes by ethenotrophs may take place under a range of redox conditions of aquifers and coincide with high ethene and VC concentrations.

Hexachlorocyclohexane isomers (HCHs) are one of the most ubiquitous and most easily detected organochlorine pesticides in environmental samples. This global distribution is enabled by HCH persistence. Moreover, HCH tends to bioaccumulate in human and animal adipose tissue. Since certain HCHs cause central nervous system, reproductive, and other endocrine damages, there is a necessity of a suitable remediation method to remove HCH from contaminated groundwater and soil. This study was conducted to evaluate the potential of peroxymonosulfate (Oxone) induced by cobalt salt (Co(NO₃)₂; Co(II)) to degrade HCHs. Cobalt(II) nitrate has been chosen instead of cobalt(II) chloride (which presents better activation properties for Oxone) in order to avoid an excess of chloride interference and more additional chlorination by-products. The optimal conditions (oxidant dose as well as cobalt dose) were determined for spiked water with HCH (0.85 μM of summed HCH isomers). Optimal oxidant dose was established by running a test with three different Oxone concentrations (molar ratio of Oxone:Co(NO₃)₂—1:0.1): 0.06, 0.6, and 6 mM. Degradation curves of summed HCH isomers were fitted into the pseudo-first-order kinetic model, and reaction rates are shown to be 0.03, 0.31, and 0.55 min⁻¹ for doses 0.06, 0.6, and 6 mM, respectively. Further experiments were carried out to determine the optimal Oxone:Co(NO₃)₂ molar ratio. Effectiveness of HCHs decontamination by Oxone:Co(NO₃)₂ in various molar ratios was in the order 1:0.1 > 1:1 > 1:0.01 > 1:0.001. It was observed that surplus of Co(NO₃)₂ can slow down the degradation rate constants. A reaction between sulfate radicals and Co(NO₃)₂ could be responsible for this phenomenon, which can lead to the formation of sulfate ions without HCHs oxidation. In addition, tests with higher HCH dose (close to the solubility limit) were carried out to determine by-products of decontamination. In these tests 2,4,6-trichlorophenol (2,4,6-TCP) was found to be the major intermediate of HCH isomers degradation. Trace levels of the trichlorobenzene (TCB), tetrachlorophenol (TeCP), and pentachlorophenol (PCP) were detected as well. The study revealed that Oxone induced by Co(II) shows a high degradation rate with HCH isomers, which can make it an attractive method for HCHs decontamination in the future.

Electrospun polyetherimide (PEI) nanofibres were fixed on a steel wire solid phase microextraction (SPME) assembly. The basic properties of the prepared nanofibres were determined by thermogravimetry, differential scanning calorimetry, adsorption, and SEM. The analytical performance of prepared PEI SPME fibres was compared with three commercially available SPME fibres, 7 μm PDMS, 100 μm PDMS, and DVB/Carboxene/PDMS. As model water pollutants, persistent organochlorinated pesticides hexachlorocyclohexanes (HCH) and chlorobenzene (ClB) were chosen as model water pollutants. The fibres were compared in the headspace- (HS-) SPME mode of GC-MS/MS instrumentation. The comparison omitted other method parameters and focused exclusively on the extraction time variability. Lab-made PEI SPME fibres showed significantly better response for the target compounds than the other tested fibres from industrial production. Based on the results, the extraction time could be shortened from 50 to 10 min, if PEI SPME fibres were used as a modification of existing analytical protocol.