The mining industry, including hard-coal mining, has a significant and multifaceted impact on all components of the environment. One of the factors is the production of various types of waste which, due to their physico-chemical and ecotoxic properties, do not always pose a threat to the environment and can be used in various ways. Such treatment of waste perfectly fits into the concept of the circular economy through the protection of natural resources and the maximum re-use of waste. One of the wastes generated by hard-coal mines is coal sludge from the purification of underground water in surface settling tanks. The article presents the results of research on the physico-chemical and phytotoxic properties of carbon sludges from two settling tanks with regard to assessing the possibility of their re-use in the reclamation of degraded areas. These sludges contain mainly sand fractions. An analysis of their chemical composition revealed the presence of heavy metals. Leachability studies have shown that despite the high concentrations of metals, a small quantity of these metals passes into the solution. In this respect, therefore, they do not pose a threat to the environment. However, a threat may result from the presence of chlorides and sulphates, the amounts of which are influenced by, among other factors, the time of waste storage in the settling tank. Phytotoxicity tests performed on garden cress ( Lepidium sativum) did not show a toxic effect at any concentration of the water extract. In addition, for one of the sludges, water extracts with concentrations starting from 12.5 and 50% stimulated the growth of the plant’s shoots and roots, respectively. The results show that the tested coal sludges may be used in appropriate doses for reclamation work, for example, when establishing a plant cover.

Ecotoxicological biotests were applied in order to evaluate their suitability as early warning systems in the continuous monitoring of lowland shallow dam reservoirs located in Central Europe. The following biotests were used: Daphtoxkit F™magna, Algaltoxkit F™, Ostracodtoxkit F, Phytotoxkit and MARA Test. The experiment was conducted from July 2010 to December 2012 in Goczalkowice Reservoir (the Vistula River, Poland), serving as a model. For the analysis, 41 out of 52 measured water indices were used to assess its toxicity to living organisms. The results of biotests were correlated with 41 hydrochemical indices of water quality. The pattern of relationships among the result of biotest and hydrochemical indices as well as Factor Analysis (FA) and Primary Component Analysis (PCA) revealed that: i) signs of ecotoxicity detected with biotests were associated with either low fl ow periods or spring surface runoff of water; ii) single events of increased ecotoxicity in the depression areas behind saddle dam pump stations appearedafter high fl ow periods; iii) elevated toxicity was accompanied by high concentrations of dissolved and suspended substances; iv) FA and PCA demonstrated correlations among the results of biotests and damming parameters, water conductivity, alkali and transitory metal metals (Ca, Fe, Cu, Zn), and several forms of nitrogen phosphorous and carbon compounds concentration. The relationships suggest that batteries of biotests may serve as a cost-eff ective tool for continuous monitoring of water quality in dam reservoirs and can detect eff ects of extreme hydrologic events, local toxic discharges, and signs of the trophic status of the reservoirs

The aim of the study was to determine the toxicity of the extract obtained from the cyanobacterial cells derived from the waters of Zemborzycki dam reservoir with use of a battery of biotests. The taxonomic identification of the bloom-forming cyanobacteria revealed high abundance of Aphanizomenon flos-aquae and Dolichospermum spp. (Anabaena spp.) and in a lower degree of Microcystis aeruginosa and Planktothrix agardhii. In the extract obtained from concentrated cyanobacterial cells, hepatotoxin microcystin-LR at a concentration of 22.89 ± 3.74 μg/L and neurotoxin Antx-a at 13.02 ± 0.01 μg/L have been detected. Toxicity of the extract was evaluated with the following assays: Daphtoxkit F magna with the crustacean Daphnia magna, Thamnotoxkit F with the crustacean Thamnocephalus platyurus, Rotoxkit F with the rotifer Brachionus calyciflorus and Protoxkit F with ciliate Tetrahymena thermophila. The most sensitive organism among all studied was T. platyurus for which EC50 was estimated to be 1.2% of the initial extract concentration. On the basis of the highest obtained value of the toxicity unit (TU = 83) the studied sample was classified to the IV class, which is of high acute toxicity. Additionally, it was found that reactivity on cyanobacterial products differs greatly among organisms used in bioassays, which indicate the need for using a set of biotests.