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During production of γ-hexachlorocyclohexane (γ-HCH), thousands of tons of other isomers were synthesized as byproducts, and after dumping represent sources of contamination for the environment. Several microbes have the potential for aerobic and anaerobic degradation of HCHs, and zero-valent iron is an effective remediation agent for abiotic dechlorination of HCHs, whereas the combination of the processes has not yet been explored. In this study, a sequence of anoxic/oxic chemico-biological treatments for the degradation of HCHs in a real extremely contaminated soil (10-30 g/kg) was applied. Approximately 1500 kg of the soil was employed, and various combinations of reducing and oxygen-releasing chemicals were used for setting up the aerobic and anaerobic phases. The best results were obtained with mZVI/nZVI, grass cuttings, and oxygen-releasing compounds. In this case, 80 % removal of HCHs was achieved in 129 days, and 98 % degradation was achieved after 1106 days. The analysis of HCHs and their transformation products proved active degradation when slight accumulation of the transformation product during the anaerobic phase was followed by aerobic degradation. The results document that switching between aerobic and anaerobic phases, together with the addition of grass, also created suitable conditions for the biodegradation of HCHs and monochlorobenzene/benzene by microbes.

Mixture toxicity, including agonistic and antagonistic effects, is an unrevealed environmental problem. Estrogenic endocrine disruptors are known to cause adverse effects for aquatic biota, but causative chemicals and their contributions to the total activity in sewage sludge remain unknown. Therefore, advanced analytical methods, a yeast bioassay and mixture toxicity models were concurrently applied for the characterization of 8 selected sludges with delectable estrogenic activity (and 3 sludges with no activity as blanks) out of 25 samples from wastewater treatment plants (WWTPs). The first applied full logistic model adequately explained total activity by considering the concentrations of the monitored compounds. The results showed that the activity was primarily caused by natural estrogens in municipal WWTP sludge. Nevertheless, activity in a sample originating from a car-wash facility was dominantly caused by partial agonists - nonylphenols - and only a model enabling prediction of all dose-response curve parameters of the final mixture curve explained these results. Antiestrogenic effects were negligible, and effect-directed analysis identified the causative chemicals.

A low-permeability locality with heterogeneous geology contaminated primarily by tetrachloroethene (PCE) present partially in the free phase in the unsaturated zone was treated on a pilot scale via direct push pneumatic fracturing combined with the hydraulic delivery of a remediation suspension consisting of milled iron, sulphidated nanosized zerovalent iron and sand in guar gum solution. Afterwards, a whey solution was injected into the fractures as a carbon source for bacteria. The unsaturated and saturated zones were treated. Long-term monitoring of the groundwater revealed that the abiotic reduction of PCE and trichloroethene was the dominant remediation processes for several months after the injections. A complex microbial consortium was developed that was capable of effective, long-term chlorinated ethenes (ClE) dechlorination. The consortium consisted mainly of Dehalococcoides but also of other anaerobic bacterial strains capable of partial dechlorination of ClE, including the sulphate-reducing bacteria; Geobacter and Desulfitobacterium. The average chlorine number in the groundwater decreased from 3.65 to 1.38 within 2.5 years after the injections, while the average ClE concentration increased from 13.5 to 31.5 mg L-1 because of the substantial acceleration of the ClE mass-transfer to the groundwater caused by the treatment. The remediation processes remained fully active for 2.5 years.

The objective of this work was to test the PCB-degrading abilities of two white-rot fungi, namely Pleurotus ostreatus and Irpex lacteus, in real contaminated soils with different chemical properties and autochthonous microflora. In addition to the efficiency in PCB removal, attention was given to other important parameters, such as changes in the toxicity and formation of PCB transformation products. Moreover, structural shifts and dynamics of both bacterial and fungal communities were monitored using next-generation sequencing and phospholipid fatty acid analysis. The best results were obtained with P. ostreatus, which resulted in PCB removals of 18.5, 41.3 and 50.5% from the bulk, top (surface) and rhizosphere, respectively, of dumpsite soils after 12 weeks of treatment. Numerous transformation products were detected (hydoxylated and methoxylated PCBs, chlorobenzoates and chlorobenzyl alcohols), which indicates that both fungi were able to oxidize and decompose the aromatic moiety of PCBs in the soils. Microbial community analysis revealed that P. ostreatus efficiently colonized the soil samples and suppressed other fungal genera. However, the same fungus substantially stimulated bacterial taxa that encompass putative PCB degraders. The results of this study finally demonstrated the feasibility of using this fungus for possible scaled-up bioremediation applications.

The paper describes a pilot remediation test combining two Cr(VI) geofixation methods - chemical reduction by nanoscale zero-valent iron (nZVI) and subsequent biotic reduction supported by whey. Combination of the methods exploited the advantages of both - a rapid decrease in Cr(VI) concentrations by nZVI, which prevented further spreading of the contamination and facilitated subsequent use of the cheaper biological method. Successive application of whey as an organic substrate to promote biotic reduction of Cr(VI) after application of nZVI resulted in a further and long-term decrease in the Cr(VI) contents in the groundwater. The effect of biotic reduction was observed even in a monitoring well located at a distance of 22 m from the substrate injection wells after 10 months. The results indicated a reciprocal effect of both the phases - nZVI oxidized to Fe(III) during the abiotic phase was microbially reduced back to Fe(II) and acted as a reducing agent for Cr(VI) even when the microbial density was already low due to the consumed substrate. Community analysis with pyrosequencing of the 16S rRNA genes further confirmed partial recycling of nZVI in the form of Fe(II), where the results showed that the Cr(VI) reducing process was mediated mainly by iron-reducing and sulfate-reducing bacteria.

We investigated the abilities of several perspective ligninolytic fungal strains to degrade 12 mono-, di- and trichloro representatives of chlorobenzoic acids (CBAs) under model liquid conditions and in contaminated soil. Attention was also paid to toxicity changes during the degradation, estimated using two luminescent assay variations with Vibrio fischeri. The results show that almost all the fungi were able to efficiently degrade CBAs in liquid media, where Irpex lacteus, Pycnoporus cinnabarinus and Dichomitus squalens appeared to be the most effective in the main factors: degradation and toxicity removal. Analysis of the degradation products revealed that methoxy and hydroxy derivatives were produced together with reduced forms of the original acids. The findings suggest that probably more than one mechanism is involved in the process. Generally, the tested fungal strains were able to degrade CBAs in soil in the 85-99% range within 60 days. Analysis of ergosterol showed that active colonization is an important factor for degradation of CBAs by fungi. The most efficient strains in terms of degradation were I. lacteus, Pleurotus ostreatus, Bjerkandera adusta in soil, which were also able to actively colonize the soil. However, in contrast to P. ostreatus and I. lacteus, B. adusta was not able to significantly reduce the measured toxicity.

Aim of this work was to investigate the ability of Lentinus (Panus) tigrinus to degrade and detoxify a chlorobenzoate (CBA) mixture composed of mono-, di- and tri-chlorinated isomers. The degradation process was investigated as a function of both the growing medium ( i.e. low N Kirk's and malt extract-glucose medium) and cultivation conditions ( i.e. stationary and shaken cultures). The majority of CBAs were quantitatively degraded within the early 15 d from spiking with the notable exception of the double ortho -chlorinated compounds, 2,6-di-, 2,3,6-tri- and 2,4,6-tri-CBA. Analysis of the degradation intermediates indicated the occurrence of side chain reduction, hydroxylation and methylation reactions. Although CBAs stimulated laccase production, in vitro experiments with a purified L. tigrinus laccase isoenzyme demonstrated its inability to participate in the initial attack on CBAs even in the presence of redox mediators; similar results were found with a Mn-peroxidase isoenzyme. Conversely, prompt degradation was observed upon 1 h incubation of CBAs with a purified microsomal fraction containing cytochrome P-450 monooxygenase. The nature of some reaction products ( i.e. hydroxylated derivatives), the dependency of the reaction on NADPH and its susceptibility to either CO or piperonyl butoxide inhibition confirmed the involvement of L. tigrinus cytochrome P-450 in the early steps of CBA degradation.

Sequential supercritical fluid extraction together with a two-site desorption model were employed to estimate the bioaccessible fraction of polycyclic aromatic hydrocarbons (PAHs) in four historically contaminated soils. The ecotoxicity of the soils was assayed by four different contact tests. The same soils were exposed to exhaustive extraction and the extracts were returned to the soils to ensure total 100% bioaccessibility of the pollutants. Then the soils were assayed again. Statistical evaluation revealed that the predicted bioaccessible PAHs generally correlated with the ecotoxicity responses of the tests. The estimated bioaccessible fractions varied from 10 to 98%. This value increased for PAHs with higher lipophilicity and showed no correlation with the organic carbon content in the soils. The ecotoxicity tests in the study indicated different sensitivity toward PAHs and the tests employing Heterocypris incongruens and Eisenia fetida were found to be more suitable than Lemna minor and Vibrio fischeri. Mortality and growth inhibition of ostracods correlated with all the types of PAHs and earthworm growth inhibition and mortality were preferentially sensitive to PAHs with only 3–4 aromatic rings. Determination of the biota-soil accumulation factors indicated that the earthworm growth inhibition corresponded to increased accumulation of PAHs in the earthworm tissue.