Long-term and seasonal trends of water parameters in the karst riverine catchment and general literature overview based on CiteSpace.

Although Europe is the continent with the highest proportion of karst areas, where hydrological systems are essential but extremely sensitive, data on the ecological status of karst riverine catchments are scarce. The aim of the present study was to assess the spatial and temporal (long-term and seasonal) variability of the physico-chemical and organic water parameters in the headwaters of the Krka River and its tributaries, as representatives of a typical karst ecosystem, situated in one of the largest karst areas in Europe, Dinarides in Croatia. It is affected in its upper reaches by improperly treated wastewaters, so anthropogenic influences and ecological status were estimated with the aim to present consequences of pollution exposure and importance of strict monitoring of such sensitive karst ecosystems worldwide. Results indicated degraded water quality, poor ecological status, and disturbed seasonal fluctuations at wastewater-influenced sites, primarily due to high levels of nutrients and organic matter. However, improvement was observed downstream in the Krka National Park, confirming the self-purification as important processes in dynamic karst rivers. Natural seasonality, observed at sites without wastewater influence, was mainly driven by fluctuations in water levels and primary production during the year. Literature analysis by CiteSpace pointed to scarce data on this topic worldwide (China and the USA account for 49% of all publications) and in Europe (34%). Therefore, such study is a valuable contribution in presenting the long-term and seasonal variability of ecological water parameters and in providing a more comprehensive understanding of the health of catchment under influence of multiple stressors.

Effects of magnesium, chromium, iron and zinc from food supplements on selected aquatic organisms.

The aim of this study was to determine the effect of uncontrolled environmental disposal of food supplements containing magnesium (Mg), chromium (Cr), iron (Fe) and zinc (Zn) on selected aquatic organisms including freshwater algae Scenedesmus subspicatus and Raphidocelis subcapitata, water flea Daphnia magna and duckweed Lemna minor. Thirty different food supplements containing Mg, Cr, Fe and Zn were analyzed. Results were expressed as effective concentration 50 (EC50), i.e. growth inhibiting Mg, Cr, Fe and Zn (mg/L) concentration immobilizing 50% of treated organisms. Particular metal EC50 differed significantly (p < 0.001) among study organisms, as follows (in ascending order): Scenedesmus subspicatus EC50 Fe (median 46.9 mg/L) < Zn (59.8 mg/L) < Mg (73.0 mg/L) < Cr (88.1 mg/L) (KW-H(3;120) = 36.856; p < 0.001); Raphidocelis subcapitata EC50 Fe (median 44.9 mg/L) < Zn (52.6 mg/L) < Mg (62.2 mg/L) < Cr (76.8 mg/L) (KW-H(3;120) = 44.0936; p < 0.001); Daphnia magna EC50 Zn (median 59.4 mg/L) < Cr (79.2 mg/L) < Fe (80.8 mg/L) Mg (82.0 mg/L) (KW-H(3;120) = 39.2637; p < 0.001); and Lemna minor EC50 Zn (median 131.0 mg/L) < Fe (186.8 mg/L) < Mg (192.5 mg/L) < Cr (240.4 mg/L) (KW-H(3;120) = 58.6567; p < 0.001). Uncontrolled environmental disposal of food supplements containing Mg, Cr, Fe and Zn exerts adverse effects on aquatic organisms. Therefore, legal provisions should regulate both the utilization and disposal of food supplements into the environment.

Toxicological and chemical assessment of arsenic-contaminated groundwater after electrochemical and advanced oxidation treatments.

Owing to its proven toxicity and mutagenicity, arsenic is regarded a principal pollutant in water used for drinking. The objective of this study was the toxicological and chemical evaluation of groundwater samples obtained from arsenic enriched drinking water wells before and after electrochemical and ozone-UV-H2O2-based advanced oxidation processes (EAOP). For this purpose, acute toxicity test with Daphnia magna and chronic toxicity test with Lemna minor L. were employed as well as in vitro bioassays using human peripheral blood lymphocytes (HPBLs). Several oxidative stress parameters were estimated in L.minor. Physicochemical analysis showed that EAOP treatment was highly efficient in arsenic but also in ammonia and organic compound removal from contaminated groundwater. Untreated groundwater caused only slight toxicity to HPBLs and D. magna in acute experiments. However, 7-day exposure of L. minor to raw groundwater elicited genotoxicity, a significant growth inhibition and oxidative stress injury. The observed genotoxicity and toxicity of raw groundwater samples was almost completely eliminated by EAOP treatment. Generally, the results obtained with L. minor were in agreement with those obtained in the chemical analysis suggesting the sensitivity of the model organism in monitoring of arsenic-contaminated groundwater. In parallel to chemical analysis, the implementation of chronic toxicity bioassays in a battery is recommended in the assessment of the toxic and genotoxic potential of such complex mixtures.

Assessment of acrylamide toxicity using a battery of standardised bioassays.

Acrylamide is a monomer widely used as an intermediate in the production of organic chemicals, e.g. polyacrylamides (PAMs). Since PAMs are low cost chemicals with applications in various industries and waste- and drinking water treatment, a certain amount of non-polymerised acrylamide is expected to end up in waterways. PAMs are non-toxic but acrylamide induces neurotoxic effects in humans and genotoxic, reproductive, and carcinogenic effects in laboratory animals. In order to evaluate the effect of acrylamide on freshwater organisms, bioassays were conducted on four species: algae Desmodesmus subspicatus and Pseudokirchneriella subcapitata, duckweed Lemna minor and water flea Daphnia magna according to ISO (International Organization for Standardisation) standardised methods. This approach ensures the evaluation of acrylamide toxicity on organisms with different levels of organisation and the comparability of results, and it examines the value of using a battery of low-cost standardised bioassays in the monitoring of pollution and contamination of aquatic ecosystems. These results showed that EC50 values were lower for Desmodesmus subspicatus and Pseudokirchneriella subcapitata than for Daphnia magna and Lemna minor, which suggests an increased sensitivity of algae to acrylamide. According to the toxic unit approach, the values estimated by the Lemna minor and Daphnia magna bioassays, classify acrylamide as slightly toxic (TU=0-1; Class 1). The results obtained from algal bioassays (Desmodesmus subspicatus and Pseudokirchneriella subcapitata) revealed the toxic effect of acrylamide (TU=1-10; Class 2) on these organisms.

The efficiency of combined CaO/electrochemical treatment in removal of acid mine drainage induced toxicity and genotoxicity.

Acid mine drainage (AMD) is a by-product of the mining industry that has a detrimental effect on aquatic plant and animal life due to high load of heavy metals and sulfates. In the present study, the toxic and genotoxic potential of AMD prior to and following combination of neutralization/electrocoagulation processes was evaluated using several bioassays and selected parameters. Regardless of pH correction of AMD prior to Daphnia bioassay, high acute toxicity was observed in Daphnia magna. The mine leachate also induced strong phyto-, cyto- and genotoxicity to Allium cepa roots. Short term exposure to AMD inhibited duckweed growth and chlorophyll a content and simultaneously promoted lipid peroxidation and DNA damage despite duckweed capability to upregulate antioxidative defense mechanisms. The results show that observed (geno)toxicity could be related to oxidative stress most probably induced by toxic metal action. However, influence of low pH as a contributing factor in the phytotoxicity of AMD cannot be excluded. The application of combined treatment eliminated genotoxicity and was highly efficient in reducing toxicity of AMD. Thus, the method seems to be suitable for treatment of AMD waters enabling their safe discharge to an aquatic environment.

Genotoxicity monitoring of freshwater environments using caged crayfish (Astacus leptodactylus).

Genotoxicity of freshwater pollution was assessed by measuring DNA damage in haemocytes of caged freshwater crayfish Astacus leptodactylus by the means of Comet assay and micronucleus test, integrated with the measurements of physiological (total protein concentration) and immunological (total haemocyte count) haemolymph parameters as biomarkers of undergone stress. Crayfish were collected at the reference site (River Mreznica) and exposed in cages for 1 week at three polluted sites along the Sava River (Zagreb, Sisak, Krapje). The long term pollution status of these locations was confirmed by chemical analyses of sediments. Statistically significant increase in DNA damage measured by the Comet assay was observed at all three polluted sites comparing to the crayfish from reference site. In addition, native crayfish from the mildly polluted site (Krapje) cage-exposed on another polluted site (Zagreb) showed lower DNA damage than crayfish from the reference site exposed at the same location indicating adaptation and acclimatisation of crayfish to lower levels of pollution. Micronuclei induction showed similar gradient of DNA damage as Comet assay, but did not reach the statistical significance. Observed increase in total haemocyte count and total protein content in crayfish from polluted environments in the Sava River also confirmed stress caused by exposure to pollution. The results of this study have proved the applicability of caging exposure of freshwater crayfish A. leptodactylus in environmental genotoxicity monitoring using Comet assay and micronucleus test.

Aporrectodea caliginosa, a suitable earthworm species for field based genotoxicity assessment?

There is a growing interest for the application of biomakers to field-collected earthworms. Therefore we have evaluated the usability of native populations of endogeic, widely distributed earthworm Aporrectodea caliginosa in the assessment of soil genotoxicity using the Comet assay. Validation of the Comet assay on earthworm coelomocytes has been established using commercially available Eisenia fetida exposed to copper, cadmium, and pentachlorophenol, along with A. caliginosa exposed to copper in a filter paper contact test. Neutral red retention time (NRRT) assay was conducted on copper exposed and field-collected earthworms. Significant DNA and lysosomal damage was measured using Comet and NRRT assays in native populations of A. caliginosa sampled from the polluted soils in the urban area in comparison to the earthworms from the reference site. The results of this study confirm the employment of A. caliginosa as a suitable species for the in situ soil toxicity and genotoxicity field surveys.