In this master's thesis, we conducted a review of the literature to assess the harmful effects of selected heavy metals. Subsequently, after conducting measurements in the Drtijščica watercourse, performing a toxicity test on the common duckweed (Lemna minor), and measuring total organic carbon (TOC), we evaluated their negative impact on the health of the surrounding population and the environment. Samples were collected from six sampling points along the Drtijščica watercourse in Moravče, where samples had also been collected in 2020 and 2021 (in our previous diploma thesis and research work). Three sampling campaigns were conducted at approximately 3-month intervals. In the samples, we analyzed the content of arsenic, cadmium, cobalt, chromium, copper, molybdenum, nickel, lead, selenium, and zinc in terms of heavy metals. Additionally, we determined the total organic carbon (TOC) content. The analytical method used for metal content determination was ICP-OES. Furthermore, we conducted toxicity testing on Lemna minor. The results were compared with measurements from 2020 and 2021, the limit values specified in Slovenian legislation and data from the Environmental Agency of Slovenia (ARSO) for other similar watercourses. The results indicated that Drtijščica has a low content of heavy metals; only arsenic exceeded the threshold values for good chemical status. The toxicity test on Lemna minor did not indicate any signs that the surface water samples are detrimental to the growth of this plant; the specific growth rate ranged from a minimum of 0,14 day-1 to a maximum of 0,24 day-1. The measured TOC values were also within normal limits, averaging between 3,85 mg/L and 5,57 mg/L. There were no significant differences between the sampling sites. In comparison with the state of a comparable watercourse, Mlinščica, lower concentrations of heavy metals were measured in Drtijščica. Based on the obtained results, it can be concluded that the condition of the Drtijščica watercourse is good and meets the criteria for good chemical and ecological status, posing no threat to the surrounding population, animals, plants, or the broader environment.
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