Gabriela Kalčíková

Seasonal variations in municipal landfill leachate quality

Purpose – The aim of this work is to compare quality of leachates from regional municipal landfill in different seasons (dry, snowy/rainy) during a three-year monitoring period due to the fact that quality of landfill leachate can rapidly change under different conditions. Design/methodology/approach – Raw leachates were sampled prior to biological treatment at different periods of the year (November 2007, March 2008, May 2008, March 2009, and January 2010) to detect the changes in their composition due to different physico-chemical conditions at the site (temperature, moisture, etc.). Leachates were physico-chemically characterized and the toxicity of chosen leachates was assessed by a battery of biotests. Findings – Most of the investigated raw leachates exceed Slovenian effluent limits. Samples from March 2008 and March 2009 generally showed higher concentration of measured parameters and also higher toxicity. It has been confirmed that the physico-chemical parameters of leachates usually decrease duri...

Fungal and enzymatic treatment of mature municipal landfill leachate.

The aim of our study was to evaluate biotreatability of mature municipal landfill leachate by using white rot fungus and its extracellular enzymes. Leachates were collected in one active and one closed regional municipal landfill. Both chosen landfills were operating for many years and the leachates generated there were polluted by organic and inorganic compounds. The white rot fungus Dichomitus squalens was able to grow in the mature leachate from the closed landfill and as it utilizes present organic matter as a source of carbon, the results were showing 60% of DOC and COD removal and decreased toxicity to the bacterium Aliivibrio fischeri. On the other hand, growth of the fungus was inhibited in the presence of the leachate from the active landfill. However, when the leachate was introduced to a crude enzyme filtrate containing extracellular ligninolytic enzymes, removal levels of COD and DOC reached 61% and 44%, respectively. Furthermore, the treatment led to detoxification of the leachate to the bacterium Aliivibrio fischeri and to reduction of toxicity (42%) to the plant Sinapis alba. Fungal and enzymatic treatment seems to be a promising biological approach for treatment of mature landfill leachates and their application should be further investigated.

Artemia salina acute immobilization test: a possible tool for aquatic ecotoxicity assessment

Despite the fact that the marine crustacean Artemia salina is extensively used in ecotoxicology, there is still a lack of information about its sensitivity to commonly used chemicals. In the presented study, acute toxicity of 18 commonly used chemicals - including organic solvents, industrial chemicals, metals and inorganic compounds - to A. salina was evaluated. A. salina showed a range of sensitivities to tested chemicals. Regarding all of the investigated organics, phenolic compounds expressed the highest toxicity to A. salina. Nitrite and mercury were the most toxic inorganic substances applied in the study. On the other hand, dimethyl sulfoxide, nitrate and ammonium were the least toxic. The possibility to use A. salina for interspecies correlation was assessed by comparison of sensitivities of different organisms (bacteria, fish, crustacean) to organic compounds. Correlation between various species was observed, especially between A. salina and fish. Due to the strong relation between toxicity and the logarithm of the octanol/water partition coefficient logP(OW,) lipophilicity was found to be the main factor influencing toxicity of the chosen organic compounds. No significant correlation between toxicity to A. salina and physico-chemical parameters of metals was observed.

Combined effect of UV-irradiation and TiO2-nanoparticles on the predator–prey interaction of gammarids and mayfly nymphs

Although nanoparticle production and application increases continuously, their implications in species interactions, especially in combination with other environmental stressors, are rarely assessed. Therefore, the present study investigated the influence of 2 mg/L titanium dioxide nanoparticles (nTiO2; <100 nm) on the interaction between the prey Ephemerella ignita (Ephemeroptera) and the predator Gammarus fossarum (Amphipoda) over 96 h considering UV-irradiation at field relevant levels (approximately 11.4 W/m(2)) as an additional environmental factor (n = 16). At the same time, gammarids consumption of an alternative food source, i.e. leaf discs, was assessed. All endpoints covered were not affected by nTiO2 alone, while the combination of nTiO2 and UV caused a reduction in gammarids predation (68%), leaf consumption (60%) and body weight (22%). These effects were most likely triggered by the UV-induced formation of reactive oxygen species by nTiO2. The present study, hence, highlights the importance to cover UV-irradiation during the risk assessment of nanoparticles.

A case study to optimise and validate the brine shrimp Artemia franciscana immobilisation assay with silver nanoparticles: The role of harmonisation☆

Brine shrimp Artemia sp. has been recognised as an important ecotoxicity and nanotoxicity test model organism for salt-rich aquatic environments, but currently there is still no harmonised testing protocol which would ensure the comparable results for hazard identification. In this paper we aimed to design the harmonised protocol for nanomaterial toxicity testing using Artemia franciscana and present a case study to validate the protocol with silver nanoparticles (AgNPs). We (i) revised the existing nanotoxicity test protocols with Artemia sp. (ii) optimised certain methodological steps based on the experiments with AgNPs and potassium dichromate (K2Cr2O7) as a soluble reference chemical and (iii) tested the optimised protocol in an international inter-laboratory exercise conducted within the EU FP7 NanoValid project. The intra- and inter-laboratory reproducibility of the proposed protocol with a soluble reference chemical K2Cr2O7 was good, which confirms the suitability of this assay for conventional chemicals. However, the variability of AgNPs toxicity results was very high showing again that nanomaterials are inherently challenging for toxicity studies, especially those which toxic effect is linked to shed metal ions. Among the identified sources for this variability were: the hatching conditions, the type of test plate incubation and the illumination regime. The latter induced variations assumingly due to the changes in bioavailable silver species concentrations. Up to our knowledge this is the first inter-laboratory comparison of the Artemia sp. toxicity study involving nanomaterials. Although the inter-laboratory exercise revealed poor repeatability of AgNPs toxicity results, this study provides valuable information regarding the importance of harmonisation of all steps in the test procedure. Also, the presented AgNPs toxicity case study may serve as a platform for further validation steps with other types of NMs.

The impact of humic acid on chromium phytoextraction by aquatic macrophyte Lemna minor.

Studies assessing chromium phytoextration from natural waters rarely consider potential implications of chromium speciation in the presence of ubiquitous humic substances. Therefore, the present study investigated the influence of environmentally relevant concentration of humic acid (TOC = 10 mg L(-1)) on chromium speciation (Cr = 0.15 mg L(-1)) and consequently on phytoextraction by aquatic macrophyte duckweed Lemna minor. In absence of humic acid, only hexavalent chromium was present in water samples and easily taken up by L. minor. Chromium uptake resulted in a significant reduction of growth rate by 22% and decrease of chlorophyll a and chlorophyll b contents by 48% and 43%, respectively. On the other hand, presence of humic acid significantly reduced chromium bioavailability (57% Cr uptake decrease) and consequently it did not cause any measurable effect to duckweed. Such effect was related to abiotic reduction of hexavalent chromium species to trivalent. Hence, findings of our study suggest that presence of humic acid and chromium speciation cannot be neglected during phytoextraction studies.

Application of multiple toxicity tests in monitoring of landfill leachate treatment efficiency

Leachate from a closed landfill used for co-disposal of municipal and tannery waste was submitted to coagulation treatment, air stripping, adsorption on granular activated carbon, and Fenton oxidation with the aim to reduce toxicity of the leachate. Optimal operational conditions for each process were identified. The performance of the treatment was monitored by determination of organic matter (COD, DOC, BOD5), inorganic components (N-NH4+, Cl−, alkalinity, metals), organic compounds (BTEX, PAHs, PCBs, OCPs) while changes in toxicity were followed by multiple toxicity tests. Among the applied treatment techniques, adsorption on granular activated carbon was the most efficient method for removal of organic matter and metals while air stripping was the most efficient for removal of N-NH4+ and reduction of toxicity. Lower reduction of organic matter content and toxicity was obtained during coagulation treatment. Fenton oxidation was effective for removal of COD; however, it negatively affected toxicity reduction. The combination of adsorption on granular activated carbon and air stripping led to an appreciable reduction of organic and inorganic pollutants and to leachate detoxification. Application of bioassays was helpful for assessing suitability of treatment methods and demonstrated that they are, together with physicochemical parameters, an indispensable part for monitoring of treatment efficiency.

Aerobic and anaerobic biodegradation potential of leachate from old active landfill

AbstractA common problem of biological treatment of landfill leachates is high toxicity and low biodegradability. Leachates from old landfills do not exhibit high toxicity and if the landfill is still filled by waste, they may contain sufficient amounts of biodegradable organic matter. With the aim of evaluating biotreatability of leachates from old, but active landfill, aerobic and anaerobic degradation assessment procedures were carried out. Investigated leachates showed low toxicity to aerobic and anaerobic micro-organisms. During biodegradability tests, anaerobic biological treatment did not lead to measurable production of biogas. Leachates were well degraded under aerobic condition in ready (66%) and inherent (78%) biodegradability tests, while simulation test in pilot sequencing batch reactor showed that leachates can be successfully treated, mixed with sewage up to 10% v/v.

Feasibility of Carbon Nanofiber Catalyst Support for the Heterogeneous Fenton Process

AbstractThe heterogeneous Fenton oxidation reaction was investigated at two different catalytic supports including the blank alumina plates and alumina plates with thin carbon nanofiber (CNF) layer. Iron (III) oxide was used as a catalyst and propionic acid (PA) was studied as a model organic compound. A carbon nanofiber layer and a thin catalytic layer of iron (III) oxide were prepared using the chemical vapor deposition method with acetylene and ferrocene precursors. The reaction rate of heterogeneous Fenton oxidation was compared with the rate of homogeneous reaction. Obtained results indicate that the reaction rate is significantly higher at homogeneous Fenton oxidation at high temperature (70°C), however, the reaction rate for homogeneous and heterogeneous oxidation is comparable at room temperature (25°C) if carbon nanofiber support is used for the iron (III) oxide catalyst.

The use of multiwell culture plates in the duckweed toxicity test—A case study on Zn nanoparticles

Extensive production of nanomaterials of various properties needs to be coupled with rapid toxicity testing in order to provide information about their potential risks to the environment and human health. Miniaturization of toxicity tests may accelerate economical testing of nanomaterials, but is not a common practice. We describe a case study to miniaturize a commonly used toxicity test with plant duckweed Lemna minor. 6-well, 12-well and 24-well culture plates were used to assess their potential use for the duckweed toxicity test with potassium chloride as reference material. The results were compared to the standard test design using 100 mL glass beakers. The comparison showed that the best agreement was with the 6-well vessels. This set-up was further used for toxicity testing of zinc oxide nanoparticles (ZnO NP) and zinc chloride. Zinc was not adsorbed onto either glass or plastic walls of the miniaturized system. We assume that in both vessels a fast agglomeration and settling of ZnO NP took place. Linear regression and statistical testing indicated a good correlation between the toxicity results obtained in the standard test and miniaturized 6-well vessels. The miniaturization of the test system for assessing the biological effect of nanomaterials on Lemna minor could become an appropriate alternative to the traditionally used high volume vessels.