V. Tsiridis

Bioavailability and Toxicity of Heavy Metals in the Presence of Natural Organic Matter

The effect of humic acids (HA) on the toxicity of copper, zinc and lead was investigated in this study, using the photobacterium Vibrio fischeri (Microtox test) as a test organism. The metal species and the complexation capacity of HA were predicted using model WinHumicV for speciation modeling. The toxicities of copper and lead were generally comparable, while the toxicity of zinc was lower than the ones of the other two method. The toxicity of copper decreased with the addition of HA, while the toxicity of zinc remained almost constant. The complexation of Zn with HA was low. Thus the presence of HA did not significantly influence the toxicity of Zn. For Cu and Zn, the free metal ion species showed to be basically responsible for the toxicity of these metals, while for Pb the chlorocomplexes and Pb-HA complexes contributed to the toxicity of Pb, indicating that the toxicity of heavy metals depends not only on the free metal ion species concentration but on different metal species that may be bioavailable.

Environmental hazard assessment of coal fly ashes using leaching and ecotoxicity tests

The environmental hazard of six coal fly ash samples collected from various coal incineration plants were examined in the present study, using various leaching tests along with physicochemical and ecotoxicological analyses. Physicochemical analyses indicated that the concentration of Ba, Cr, Mo, Se, sulfates and total dissolved solids (TDS) exceeded the threshold values, according to the European Council decision 2003/33/EC for inert, non-hazardous or hazardous waste. The highest sensitivity, among examined organisms, was presented by Daphnia magna and was ascribed to the lowest tolerance of the organism to Cr. The toxic effect profile of the leachates toward Vibrio fischeri revealed that its bioluminescence was significantly altered by the presence of heavy metals in the leachates (such as Cu, Ni and Zn) in low or sub-lethal doses. Although the toxicity of the leachates toward Pseudokirchneriella subcapitata was relatively high, the correlation between the toxicity and heavy metals concentration was rather poor, indicating the significance of the bioavailability of constituents and the importance of toxicity testing. Based on the classification of the samples resulted by physicochemical analyses of the leachates and the results of ecotoxicity tests, Physicochemical and Ecotoxicological indices were also defined, for an overall evaluation of the environmental impact assessment of fly ashes. The suggested indices showed that ecotoxicity tests were in some cases inconsistent with the outcome of waste classification based on physicochemical analyses. Moreover, the examination of leaching protocols and obtained results showed that one stage leaching test (L/S=10 L/kg) underestimated the fly ash classification, when compared with the two stage test EN 12457-3 at the cumulative ratio L/S=10 L/kg. In addition, the application of availability test NEN 7341 provided useful results about the ecotoxicity wastes. Thus, NEN 7341 is strongly suggested for the implementation of such studies, since the bioavailability of constituents may not be altered by pH adjustment tactics and pH-originated toxicity effects may be avoided.

Hexavalent chromium release from lignite fly ash and related ecotoxic effects

Hexavalent chromium Cr(VI) is a pollutant of immense concern due to its high mobility to water sources and highly toxic properties. In most cases, Cr(VI) could be released from lignite fly ash in aquatic environment when fly ash comes into contact with water. In this study, the contribution of the leaching patterns and bioavailability of Cr(VI) from lignite fly ash to the overall ecotoxic properties of fly ash leachates was originally examined and leaching procedures were evaluated in this context. A series of customized leaching tests were conducted and a battery of ecotoxicity tests including the crustacean Daphnia magna and the photobacterium Vibrio fischeri was applied. The leaching of Cr(VI) was pH and liquid to solid (L/S) ratio dependent, exhibiting the highest releases at pH values between 7 and 8. At the liquid to solid ratio (L/S) equal to 100 L/kg, the (CrVI) release reached a plateau, implying the presence of diffusion constrains and/or solubility hindrances. The toxic effect of the leachates obtained under leaching at pH 7 towards D. magna was relatively high (TU = 28.6 (23.8–35.7) at L/S = 10 L/kg). Interestingly, the toxicity of the leachates towards D. magna not only was significantly correlated to Cr(VI) (r = 0.961, P < 0.01), but the toxicity of the leachates (in absolute values) was matching the toxicity of the Cr(VI) revealing its remarkable contribution to the overall effect. In addition, the lower sensitivity of the bacteria V. fischeri when exposed to the leachates, along with the time dependence of the toxicity profiles supported the interpretation of the results obtained in this study.

Comparison of several toxicity tests applied to complex wastewaters and mussel biomarkers in receiving waters

In this study, the complex wastewaters/effluents discharged to coastal regions of Turkey and Greece were sampled, and various toxicity tests were applied. The bioassays used included the assessment of the luminescence inhibition of the bacterium Vibrio fisheri, the photosynthesis inhibition (14C uptake rate) and growth inhibition of the algal species Phaeodactylum tricornutum, and the mortality of the crustacean Artemia franciscana and rotifer Brachionus plicatilis. Additionally, “neutral red retention” and “filtration rate” sublethal biomarker techniques were performed by utilizing the mussel species Mytilus galloproviancialis, inhabiting the points of discharges in Turkey. All discharges tested were found to be acutely toxic to P. tricornutum and slightly toxic to V. fisheri, A. franciscana, and B. plicatilis. Test results showed that the 14C uptake rate toxicity test was the most sensitive one among the other bioassays. The biomarker results showed that the health status of mussels in the coastal areas decreased significantly, indicating the pollution of the receiving waters in Turkey. The conclusions drawn highlight the necessity for an intesive ecotoxicological monitoring scheme that will incorporate the most suitable bioassays and biomarkers to adequately contribute to the upgrading and maintenance of the ecological quality of the coastal waters in Greece and in Turkey. *Presented as an invited plenary lecture at “The 2nd Asian International Conference on Ecotoxicology and Environmental Safety” (SECOTOX 2004), Songkla, Thailand, 26–29 September 2004.

Implications of handling practices on the ecotoxic profile of alumina nanoparticles towards the bacteria Vibrio fischeri.

ABSTRACT The complex nature and behavior of Engineered Nanomaterials (ENMs) has led to adoption of customized experimental ecotoxicity practices that are prone to possible artefacts in the inherent toxic properties of ENMs. In addition, the lack of standardized handling procedures for the ecotoxicity testing of ENMs prevents the development of experimental protocols for regulatory purposes. In this study, a suite of techniques for dispersion of ENMs was adopted and tested for two types of surface-modified alumina nanoparticles—one hydrophobic and one hydrophilic—towards the bacteria, Vibrio fischeri. The effect of certain handling practices on the observed ecotoxic effects on V. fischeri was examined. The overall goal was to evaluate by what means the handling practices of ENMs may affect the obtained toxicity results. It was realized that the toxicity of the hydrophilic and hydrophobic ENMs was mainly affected by the centrifugation and the salinity of the tested dispersions, respectively. It is more likely that both aluminium and coating substance contributed to the overall toxicity. Toxicity results are discussed with regard to generic physicochemical characteristics of the dispersions.

Toxic and interactive toxic effects of agrochemical substances and copper on Vibrio fischeri

The toxic and interactive toxic effects of two agrochemicals (fosthiazate and metalaxyl-M) and copper were investigated in this study on the photobacterium Vibrio fischeri. The toxicities of all tested compounds were generally comparable. The order of toxicity was: copper > fosthiazate > metalaxyl-M. The interactive effects of fosthiazate and metalaxyl-M mixtures were found to be additive for most of the concentration combinations tested. For the binary mixtures of fosthiazate and copper the interactive effect was antagonistic for all concentration combinations tested. Both agrochemicals showed a similar toxic response, while the toxicity of copper increased significantly by the increase of exposure time and a steep increase of copper toxicity was observed with a small increase of its concentration.