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S-metolachlor is one of the most frequently used herbicides worldwide. However, toxicity studies of this herbicide to aquatic organisms are scarce. In the present study, two experiments were conducted to test the effects of S-metolachlor on common carp, one of the most economically important fish species, with a distribution throughout the world: (1) 96 h acute semi-static toxicity test, aiming to determine LC50; (2) a subchronic semi-static test that lasted 28 days, in which juvenile carp were exposed to 3%, 8%, and 25% of previously determined LC50—0.5 mg·L−1, 1.4 mg·L−1, and 4.1 mg·L−1, respectively. Several biomarkers were employed to assess fish responses to toxicants. Blood biochemistry analysis and nuclear alterations of erythrocytes did not show any difference among experimental groups. Semi-quantitative histopathological analysis revealed mild alterations in the gills and liver, where oedema of secondary epithelium of gills and leukocyte infiltration in liver were significantly higher in fish exposed to 1.4 mg·L−1 and 4.1 mg·L−1. Histopathological indices in liver, as well as the total histopathological index, also showed significantly higher scores in the same groups. Bioconcentration factors of S-metolachlor ranged from 3.2 to 9.4, depending on the experimental group.

Mountain ecosystems are going through changes due to numerous physical-chemical processes in the environment rather than the anthropogenic activities. Primordial radioactivity of rock and soil material migrates and fractionates in other environmental sections like waters, air and biota. Having a feature to accumulate different minerals and trace element present in soil and three substrates, fungi indicates their composition and related processes. The aim of this study is uptake of radionuclides by fungi in the schist soil of the Stara Planina, mountain famous for biodiversity as well as for enhanced natural radioactivity areas. Samples of various fungi species (stipes and cups) and their soil substrates have been collected in summer season 2019. Collected soil samples are pedologically characterized and analysed by gamma-spectrometry (HP Ge) after the secular radioactive equilibrium had been reached. Soil characterization has shown the share of coarse fragments, sand, silt and clay in the schist (shale) structure while pH value was 4.80-5.33 and organic carbon content 3.10%. The content of significant natural radionuclides 40K, 226Ra, 232Th, 238U and manmade 137Cs was (in Bq/kg) was 500±30, 27±2, 26±2, 32±4, 1.6±0.2 respectively. Dried fungi samples were analysed by gamma spectrometry showing the natural radionuclide content in wide range of values. Obtained results indicate dependence of the radionuclides uptake from the substrate on their abundance in schist soil type as well as the fungus specie physiology. Slight difference was observed in results between content in species with different types of nutrient uptake (mycorrhizal and saprobic). The 137Cs content varied from 2-20 Bq/kg. Further knowledge on the local population habits in use of edible fungi species would enable dose assessment for the representatives of the public and contribute to a further research on the Stara Planina mountain ecosystem.