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The application of biochar (the by-product of biomass pyrolysis), as a soil amendment has been accepted as a sustainable solution to improve soil quality. The current study aims to establish a decision support tool for characterizing, ranking, and selecting biochars of different origins for soil improvement, thereby contributing to the development of a systematic approach, which lacks in the existing literature.The development of a Multi-Criteria Decision Support Approach applying a banded and weighted rating and scoring system allowed the selection and ranking of various biochars suitable for improving sandy soils before application. First, 14 selected, different biochar products (produced from industrial by-products, herbaceous, wood-based and manure-based feedstocks) were characterized with several physicochemical, biological and ecotoxicological methods taking into account both the technological and the environmental efficiency aspects of biochar utilization. Then, a system for the assessment and ranking of biochars for acidic, and calcareous neutral sandy soil improvement was developed, which could be flexibly adapted to different soil problems as well. Based on their performance in the tests, scores from (−5) to (+5) were assigned to each biochar. As a result, the grain husks and paper fiber sludge biochar was ranked as the most suitable for both acidic and neutral calcareous sandy soil improvement, with 55 and 43 scores, respectively (from the maximum 100). The applicability of this innovative multicriteria scoring-ranking system, as a tool for potential biochar users, was verified in microcosms and field-scale experiments, demonstrating the positive influence of this biochar on the acidic sandy soil.

The application of Biolog EcoPlate™ for community-level physiological profiling of soils is well documented, however, the functional diversity of aquatic bacterial communities has been hardly studied. The objective of this study was to investigate the applicability of the Biolog EcoPlate™ technique and evaluate comparatively the applied endpoints, for the characterisation of the effects of metal oxide nanoparticles (MONPs) on freshwater microbial communities. Microcosm experiments were run to assess the effect of nano ZnO and nano TiO2 in freshwater at 0.8–100 mg/L concentration range. The average well colour development, substrate average well colour development, substrate richness, Shannon index and evenness, Simpson index, McIntosh index and Gini coefficient were determined to quantify the metabolic capabilities and functional diversity. Comprehensive analysis of the experimental data demonstrated that short-term exposure to TiO2 and ZnO NPs affected the metabolic activity at different extent and through different mechanisms of action. TiO2 NPs displayed lower impact on the metabolic profile showing up to 30% inhibition. However, the inhibitory effect of ZnO NPs reached 99% with clearly concentration-dependent responses. This study demonstrated that the McIntosh and Gini coefficients were well applicable and sensitive diversity indices. The parallel use of general metabolic capabilities and functional diversity indices may improve the output information of the ecological studies on microbial communities.

Red mud can be applied as soil ameliorant to acidic, sandy and micronutrient deficient soils. There are still knowledge gaps regarding the effects of red mud on the soil microbial community. The Biolog EcoPlate technique is a promising tool for community level physiological profiling. This study presents a detailed evaluation of Biolog EcoPlate data from two case studies. In experiment “A” red mud from Ajka (Hungary) was mixed into acidic sandy soil in soil microcosms at 5–50 w/w%. In experiement “B” red mud soil mixture was mixed into low quality subsoil in a field experiment at 5–50 w/w%. According to average well color development, substrate average well color development and substrate richness 5–20% red mud increased the microbial activity of the acidic sandy soil over the short term, but the effect did not last for 10 months. Shannon diversity index showed that red mud at up to 20% did not change microbial diversity over the short term, but the diversity decreased by the 10th month. 30–50% red mud had deteriorating effect on the soil microflora. 5–20% red mud soil mixture in the low quality subsoil had a long lasting enhancing effect on the microbial community based on all Biolog EcoPlate parameters. However, 50% red mud soil mixture caused a decrease in diversity and substrate richness. With the Biolog EcoPlate we were able to monitor the changes of the microbial community in red mud affected soils and to assess the amount of red mud and red mud soil mixture applicable for soil treatment in these cases.

Bacterial Quorum Sensing is a cell-to-cell communication process, in which, bacteria, performing cooperative behaviour, produce and detect extracellular signalling chemicals, to monitor cell population density. Numerous bacterial processes including bioluminescence, virulence factor production, biofilm formation etc. are known to be influenced by this bacterial communication network. Interest in QS systems has emerged in response to the fact that these processes have significant impact on the environment, human health as well as agriculture. Cyclodextrins-mediated quorum quenching is an innovative approach and the available information about their effects is very scarce. We selected Aliivibrio fischeri, a bacterium, producing light, based on Quorum Sensing, to be the first to investigate the cyclodextrins’ effect on this bioluminescence. A systematic study was performed with twelve different cyclodextrin compounds in order to determine their concentration- and time-dependent bioluminescence inhibitory effect in the A. fischeri model system. Especially high quorum quenching effect was found for α-cyclodextrin: 10 mM α-cyclodextrin at 120 min contact time which caused ~64% inhibition of bioluminescence. Experiments with the co-administration of α-cyclodextrin and N-(3-oxohexanoyl)-L-homoserine lactone, the signalling molecule of A. fischeri clearly showed, that the stimulating effect of this signal was diminished by α-cyclodextrin, suggesting, that complexation was responsible for the observed Quorum Sensing suppression. Although β-cyclodextrin and its hydroxypropyl derivative significantly inhibited bioluminescence at as low as 0.156 mM concentration, their efficiency did not reach the level of α-cyclodextrin. According to our results, the autoinducer-dependent quorum sensing mechanism in Aliivibrio fischeri was markedly inhibited, the quorum quenching effect of cyclodextrins was clearly demonstrated. The efficiency was influenced by several parameters; the size of the interior cavity, the structure and the concentration of the cyclodextrins, as well as the contact time with the cells. The application of a cyclodextrin-trap for complexation of signal molecules may be a novel, promising method for influencing QS interfering strategies, for example, to enhance the efficiency of various biotechnologies, as well as to find alternative approaches against bacterial proliferation and infections. Furthermore, our results could also serve as a basis for further research with bacterial or plant model systems, in which the same chemical signals may induce physiological responses.

Direct toxicity assessment (DTA) results provide the scale of the actual adverse effect of contaminated environmental samples. DTA results are used in environmental risk management of contaminated water, soil and waste, without explicitly translating the results into chemical concentration. The end points are the same as in environmental toxicology in general, i.e. inhibition rate, decrease in the growth rate or in yield and the ‘no effect’ or the ‘lowest effect’ measurement points of the sample dilution–response curve. The measurement unit cannot be a concentration, since the contaminants and their content in the sample is unknown. Thus toxicity is expressed as the sample proportion causing a certain scale of inhibition or no inhibition. Another option for characterizing the scale of toxicity of an environmental sample is equivalencing. Toxicity equivalencing represents an interpretation tool which enables toxicity of unknown mixtures of chemicals be converted into the concentration of an equivalently toxic reference substance. Toxicity equivalencing, (i.e. expressing the toxicity of unknown contaminants as the concentration of the reference) makes DTA results better understandable for non-ecotoxicologists and other professionals educated and thinking based on the chemical model. This paper describes and discusses the role, the principles, the methodology and the interpretation of direct toxicity assessment (DTA) with the aim to contribute to the understanding of the necessity to integrate DTA results into environmental management of contaminated soil and water. The paper also introduces the benefits of the toxicity equivalency method. The use of DTA is illustrated through two case studies. The first case study focuses on DTA of treated wastewater with the aim to characterize the treatment efficacy of a biological wastewater treatment plant by frequent bioassaying. The second case study applied DTA to investigate the cover layers of two bauxite residue (red mud) reservoirs. Based on the DTA results the necessary toxicity attenuation rate of the cover layers was estimated.

BACKGROUND Red mud is increasingly considered a valuable by-product requiring development of new re-use technologies instead of deposition as waste. This paper reports the results of a microcosm study aiming to reveal the beneficial effects of the Ajka red mud, as soil ameliorant, on a specific acidic sandy soil in eastern Hungary. RESULTS The red mud amount mixed into the sandy soil ranged between 0 and 50%. The experiment was monitored by an integrated methodology combining physical and chemical methods with biological and ecotoxicological measurements. The adverse effects of red mud were examined by ecotoxicity tests using test organisms from three trophic levels: Aliivibrio fischeri (luminescent bacterium), Sinapis alba (plant), Triticum aestivum (plant) and Tetrahymena pyriformis (unicellular animal). The results showed that red mud applied at 5% had positive effects on the degraded acidic sandy soil, significantly increasing soil pH, improving soil texture and water holding capacity. In addition, according to the ecotoxicological test results 5% w/w red mud had no significant adverse effects on the tested organisms as members of the soil ecosystem. CONCLUSION The results demonstrated the beneficial effects of red mud as an ameliorant of acidic sandy soils under continental climatic conditions. © 2016 Society of Chemical Industry

A three tiered, iterative Environmental Risk Assessment methodology, including preliminary Qualitative Risk Assessment, Quantitative Hazard Assessment and Site Specific Quantitative Risk Assessment, was established to assess the environmental risk of point and diffuse pollution of mining origin at catchment scale [1]. The model site was an abandoned Pb and Zn sulphide ore mine in Gyöngyösoroszi, Toka-valley, NE Hungary [2]. The Integrated Risk Model considers the sources identified by the GIS-based (Geographical Information System) pollution map, the transport routes shown by the GIS-based flow accumulation model and the receptors of different land uses in the catchment. The site-specific quantitative risk was characterised by the Soil Testing Triad [3]. The three elements of the Triad are: physico-chemical analyses of the soil and the contaminants, the biological characterisation and ecotoxicity testing of the contaminated soil, measuring the response of single species in laboratory bioassays, the natural response of the soil microflora and plants or the dynamic response of the whole soil in microcosms. The Triad approach strongly supports the characterisation of the site specific risk as well as the selection and planning of the suitable remediation option.

An Environmental Risk Management methodology was developed for the Toka catchment area, an abandoned base metal mining site in Gyöngyösoroszi, Hungary. The postmining activities on the Hungarian site require the management of both the point and diffuse sources. The mobile Cd and Zn content of the mine waste, soil and sediment transported by water pose the highest environmental risk in the area. The approach is „GIS based” (Geographical Information System) and „catchment scale”, using a three tiered, iterative Environmental Risk Assessment methodology. The model parameters of the metal transport were determined in leaching microcosms. The risk reduction concept aims at reducing the runoff water quantity and contamination by removal of the point sources and chemical & phytostabilisation of the residual and diffuse pollution. The planning of the field application was based on the results of the stabilisation microcosms.

Biochar produced from a wide range of organic materials by pyrolysis has been reported as a means to improve soil physical properties, fertility and crop productivity. However, there is a lack of studies on the complex effects of biochar both on the degraded sandy soil physico-chemical properties and the soil biota as well as on toxicity, particularly in combined application with fertilizer and compost. A 7-week microcosm experiment was conducted to improve the quality of an acidic sandy soil combining variations in biochar types and amounts, compost and fertilizer application rates. The applied biochars were produced from different feedstocks such as grain husks, paper fibre sludge and wood screenings. The main purpose of the microcosm experiment was to assess the efficiency and applicability of different biochars as soil amendment prior to field trials and to choose the most efficient biochar to improve the fertility, biological activity and physical properties of acidic sandy soils. We complemented the methodology with ecotoxicity assessment to evaluate the possible risks to the soil as habitat for microbes, plants and animals. There was clear evidence of biochar-soil interactions positively affecting both the physico-chemical properties of the tested acidic sandy soil and the soil biota. Our results suggest that the grain husk and the paper fibre sludge biochars applied to the tested soil at 1% and 0.5 w/w% rate mixed with compost, respectively can supply a more liveable habitat for plants and soil living animals than the acidic sandy soil without treatment.

Red mud, the by-product of aluminum production, has been regarded as a problematic residue all over the world. Its storage involves risks as evidenced by the Ajka red mud spill, an accident in Hungary where the slurry broke free, flooding the surrounding areas. As an immediate remediation measure more than 5cm thick red mud layer was removed from the flooded soil surface. The removed red mud and soil mixture (RMSM) was transferred into the reservoirs for storage. In this paper the application of RMSM is evaluated in a field study aiming at re-utilizing waste, decreasing cost of waste disposal and providing a value-added product. The purpose was to investigate the applicability of RMSM as surface layer component of landfill cover systems. The field study was carried out in two steps: in lysimeters and in field plots. The RMSM was mixed at ratios ranging between 0 and 50% w/w with low quality subsoil (LQS) originally used as surface layer of an interim landfill cover. The characteristics of the LQS+RMSM mixtures compared to the subsoil (LQS) and the RMSM were determined by physical-chemical, biological and ecotoxicological methods. The addition of RMSM to the subsoil (LQS) at up to 20% did not result any ecotoxic effect, but it increased the water holding capacity. In addition, the microbial substrate utilization became about triple of subsoil (LQS) after 10months. According to our results the RMSM mixed into subsoil (LQS) at 20% w/w dose may be applied as surface layer of landfill cover systems.

The red mud catastrophe of October 2010 in Hungary draw the attention to the problem of red mud disposal sites, storage reservoirs and other wastes of mining origin that pose severe threats to humans and the environment all over the world. Present study introduces the results of the risk assessment that supported management of the priority risks and decision making on the necessary and most efficient risk reduction measures.