Increasing use of metal and metal oxide nanoparticles [Me(O)NPs] in products means many will inevitably find their way into marine systems. Their likely fate here is sedimentation following hetero-aggregation with natural organic matter and/or free anions, putting benthic, sediment-dwelling and filter feeding organisms most at risk. In marine systems, Me(O)NPs can absorb to micro-organisms with potential for trophic transfer following consumption. Filter feeders, especially bivalves, accumulate Me(O)NPs through trapping them in mucus prior to ingestion. Benthic in-fauna may directly ingest sedimented Me(O)NPs. In fish, uptake is principally via the gut following drinking, whilst Me(O)NPs caught in gill mucus may affect respiratory processes and ion transport. Currently, environmentally-realistic Me(O)NP concentrations are unlikely to cause significant adverse acute health problems, however sub-lethal effects e.g. oxidative stresses have been noted in many organisms, often deriving from dissolution of Ag, Cu or Zn ions, and this could result in chronic health impacts.

The interactive effects of cadmium (Cd) and pyrene (Pyr) on contaminant removal from co-contaminated sediment planted with Kandelia obovata were investigated by a pot experiment. We found that dry weight of plant was significantly decreased under high level of Cd–Pyr combined stress. High Pyr caused the increase of Cd toxicity to K. obovata under high Cd stress because more Cd translocated to the plant tissues. Cd toxicity inhibited Pyr degradation in co-contaminated sediments and higher Pyr degradation was found in the rhizosphere than that in the non-rhizosphere sediment under high Cd treatment. The total number of microorganisms in sediments tended to decrease with increasing Cd under Cd–Pyr combined stress and more amount existed in the rhizosphere sediment. In conclusion, Cd and Pyr removal by K. obovata can influence interactions between these two pollutants in co-contaminated sediment. This suggests that this mangrove can effectively remedy sites co-contaminated with these two types of contamination.

Heavy metals are determinant factors in increasing environmental pollution, and chromium is considered to be of highest concern because of its genotoxicity in microorganisms, animals, and humans. Relatively few studies are focused on the injury induced in plant genetic material. Therefore, the main objective of this work was to evaluate the extent of the cytogenetic damage induced in root meristems of barley (Hordeum vulgare L.) after short-term seed exposure to 10, 100, 250, and 500 μM K₂Cr₂O₇(Cr(VI) concentration is 1.04, 10.39, 25.99, and 51.99 μg ml⁻¹) and 10, 100, 250, and 500 μM CrCl₃(Cr(III) concentration is 0.52, 5.19, 12.99, and 25.99 μg ml⁻¹). Chromium genotoxic potential was proved by significant increases in the rates of the ana-telophase chromosomal aberrations (1.3–2.3 times higher for K₂Cr₂O₇and 1.7–2.2 times higher for CrCl₃, as compared to the control; p < 0.05, p < 0.01) and of metaphase disturbances (5.0–7.5 times more numerous in chromium-treated groups than in control; p < 0.001). The pattern of the chromosomal aberrations is constituted by chromatid bridges, complex aberrations, lagging, and vagrant chromosomes, while the abnormal metaphases are c-like metaphases, sticky metaphases, and metaphases with chromosomes expulsed from equatorial plate. The mitotic indices and the growth of the barley plantlets in the early ontogeny were stimulated by chromium. The changes induced in the frequency of division stages mainly consisted in prophase and telophase accumulation and diminution of metaphase and anaphase proportion.

Investigations on the pollution of groundwater with pathogenic microorganisms, e.g. tracer studies for groundwater transport, are constrained by their potential health risk. Thus, microspheres are often used in groundwater transport studies as non-hazardous surrogates for pathogenic microorganisms. Even though pathogenic microorganisms occur at low concentrations in groundwater, current detection methods of microspheres (spectrofluorimetry, flow cytometry and epifluorescence microscopy) have rather high detection limits and are unable to detect rare events. Solid-phase cytometry (SPC) offers the unique capability of reliably quantifying extremely low concentrations of fluorescently labelled microorganisms or microspheres in natural waters, including groundwater. Until now, microspheres have been used in combination with SPC only for instrument calibration purposes and not for environmental applications. In this study, we explored the limits of the SPC methodology for its applicability to groundwater transport studies. The SPC approach proved to be a highly sensitive and reliable enumeration system for microorganism surrogates down to a minimum size of 0.5 μm, in up to 500 ml of groundwater, and 0.75 μm, in up to 1 ml of turbid surface water. Hence, SPC is proposed to be a useful method for enumerating microspheres for groundwater transport studies in the laboratory, as well as in the field when non-toxic, natural products are used.

Redox conditions play an outstanding role in controlling the behaviour of trace elements in soil environments. They are not only sensitive to water saturation but also to soil temperature because many redox reactions are mediated by microorganisms. In this study, we investigated the influence of oxidising (oxygen predominant), weakly reducing (Mnᴵᴵᴵ,ᴵⱽreduction) and moderately reducing (Feᴵᴵᴵreduction) conditions at three temperature regimes (7, 15 and 25 °C) on the solubility of ten trace elements. Multimetal-contaminated topsoil (pH 5.8) from a floodplain in Germany was investigated with the following aqua regia-soluble concentrations: Zn 903, Cu 551, Cr 488, Pb 354, Ni 93.5, As 35.7, Co 22.4, Sb 20.5, Cd 8.3 and Mo 6.5 mg kg⁻¹. Soil suspensions were held at fixed redox potential in microcosm experiments, sampled at every third day and analysed for trace elements. Time to achieve weakly and particularly moderately reducing conditions was temperature dependent and increased in the order 25 °C < 15 °C < 7 °C. Under oxidising conditions, the solubility of the trace elements was low. Reductive dissolution of Mn oxides under weakly reducing conditions was accompanied by a release of Co and Mo. Reductive dissolution of Fe oxides (and of remaining Mn oxides) under moderately reducing conditions additionally led to a release of As, Cd, Cr, Ni and Pb, whereas Cu and Zn were hardly affected. Antimony revealed a different behaviour because, after a first increase, a continuous decrease in its concentration was observed soon after the onset of weakly reducing conditions. We conclude that soil temperature should be considered as a master variable, to distinguish between weakly and moderately reducing soil conditions, and that it is necessary to keep element-specific behaviour in mind when dealing with the effects of redox conditions in soils on trace element solubility.

Microorganisms are abundant in many surface and near-surface geochemical environments. They interact with arsenic through a variety of mechanisms, including sorption, mobilisation, precipitation and redox and methylation transformation; sometimes, this is to their benefit, while other times it is to their detriment, substantially affecting the fate and transport of arsenic in the environment. Here, an attempt was made to review the current state of knowledge concerning microbial influences on arsenic transformation and retention processes at the water–solid interface with the goal to elucidate the ability of microorganisms to react with arsenic, and to quantify the role of microorganisms in the biogeochemical arsenic cycle. Such knowledge is indispensable for comprehensive understanding arsenic behaviour in the environment and support accurate assessment of the threat of arsenic contamination to human and environmental health, as well as for the development of novel technologies for arsenic bioremediation.

Textile industry is responsible for a large amount of wastewater inappropriate for both human consumption and aquatic species. Aquatic ecosystems are way more sensitive to the release of textile wastewater, and the usage of Winogradsky columns is interesting, once they are a simulated aquatic ecosystem in which the growth of algae and other microorganisms can be observed. In this research, simulated textile effluents with the dye Acid Blue 40 were treated with an electrolytic reactor, for a later ecotoxicological evaluation using Winogradsky columns. The algal and microbial population and primary production were measured. The results have shown that the electrolytic treatment was satisfactory when it comes to color removal, but the presence of the treated effluent in the Winogradsky columns changed the microecosystem. The number of algae identified decreased when exposed to certain effluents, and some algae groups even disappeared, while others such as Cyanophyceae were benefited.

Methane (CH₄) formation in wastewater treatment is linked to long residence times under anaerobic conditions such as those in sewers and primary treatment units. Emissions of this methane to the atmosphere can occur under turbulent flows and, potentially, during aeration in an activated sludge plant. An online, 8-week monitoring campaign of CH₄emissions and operational conditions was conducted to study emissions from a full-scale nitrifying activated sludge plant (ASP). Significant emissions were found throughout the aerated lane, with the highest values observed two thirds down the lane. Emissions had high diurnal and spatial variability, with values ranging from 0.3 to 24 g CH₄/h. No significant correlations were found between dissolved oxygen, aeration or influent loads. The results suggest that emissions are linked to upstream process conditions, with potential for methane generation in-lane due periods of limited oxygen availability. The dynamic oxygen profile observed suggests that aerobic and anoxic conditions coexist in the lane, leading to limited oxygen diffusion from the bulk liquid to the inner regions of the floc where anoxic/anaerobic layers may allow methanogenic microorganisms to survive. The average emission factor was 0.07 % of removed chemical oxygen demand, giving a total of 668 kg CH₄/year and 14,000 CO₂equivalents/year. The operational carbon associated with the energy requirements of the ASP increased by 5 %. With emerging legislation requiring the reporting of greenhouse gas emissions, the carbon impact may be significant, particularly as the industry moves towards a carbon-reducing future. Therefore, an adequate profiling of full-scale emissions is critical for future proofing existing treatment technologies.

Composting has been demonstrated to be effective in degrading organic pollutants (OP) whose behaviour depends on the composting conditions, the microbial populations activated and interactions with organic matters. The fate of OP during composting involves complex mechanisms and models can be helpful tools for educational and scientific purposes, as well as for industrialists who want to optimise the composting process for OP elimination. A COP-Compost model, which couples an organic carbon (OC) module and an organic pollutant (OP) module and which simulates the changes of organic matter, organic pollutants and the microbial activities during the composting process, has been proposed and calibrated for a first set of OP in a previous study. The objectives of the present work were (1) to introduce the COP-Compost model from its convenient interface to a potential panel of users, (2) to show the variety of OP that could be simulated, including the possibility of choosing between degradation through co-metabolism or specific metabolism and (3) to show the effect of the initial characteristics of organic matter quality and its microbial biomass on the simulated results of the OP dynamic. In the model, we assumed that the pollutants can be adsorbed on organic matter according to the biochemical quality of the OC and that the microorganisms can degrade the pollutants at the same time as they degrade OC (by co-metabolism). A composting experiment describing two different ¹⁴C-labelled organic pollutants, simazine and pyrene, were chosen from the literature because the four OP fractions simulated in the model were measured during the study (the mineralised, soluble, sorbed and non-extractable fractions). Except for the mineralised fraction of simazine, a good agreement was achieved between the simulated and experimental results describing the evolution of the different organic fractions. For simazine, a specific biomass had to be added. To assess the relative importance of organic matter dynamics on the organic pollutants’ behaviour, a sensitivity analysis was conducted. The sensitivity analysis demonstrated that the parameters associated with organic matter dynamics and its initial microbial biomass greatly influenced the evolution of all the OP fractions, although the initial biochemical quality of the OC did not have a significant impact on the OP evolution.

The accumulation and fraction distribution of Ni(II) in sludge was determined, and their effect on the performance of sequencing batch reactor (SBR) systems was evaluated at laboratory scale. The results showed that the removal efficiencies of substrates decreased significantly with increasing feeding concentration of Ni(II) into SBRs. The concentration of Ni(II) fed into the SBRs was significantly positively correlated with the Ni(II) contents accumulated in the sludge, while it was negatively correlated with the biomass in the SBRs. The accumulated Ni(II) in the sludge was distributed mainly in the available fraction, accounting for 75.8–90.0 % of the total Ni(II) content. The accumulated content of Ni(II) in each sludge fraction could be predicted satisfactorily by the feeding Ni(II) concentrations in the solutions. As compared with the total contents and other chemical fractions, Ni(II) in the oxidizable fraction in sludge exhibited more important inhibition effects on sludge microorganisms in the SBRs.