## 4 Results and Discussion
### PAH Toxicity  
Some of the PAHs are believed to have carcinogenic and mutagenic effects on living organisms. Among them, BaP is considered especially hazardous and belongs to the 1 st hazard class, which causes cancer [69]. The maximum permissible concentrations for snow cover have not been established so far; therefore, water quality standards were applied in this study. The European Union (EU) established an environmental quality standard for BaP in inland surface waters, specifying an annual average value of 0.17 ng/L and a maximum allowable concentration of 270 ng/L, as outlined in Directive 2013/39/EU of the European Parliament and Council [70]. The BaP equivalent toxicity (\(BaP_{\text{TEQ}}\)) was calculated using the toxic equivalency factor (TEF) method [71]. The toxic equivalency of a mixture is presented as the sum of the concentrations of individual compounds (Ci) multiplied by their respective TEF:  
\[BaP_{TEQ}=\sum(C_{i}\;*\;TEF_{i})\]  
where TEFi values are as follows: Ph (0.001), Ant (0.01), BaA (0.1), Flt (0.001), Pyr (0.01), Chr (0.01), BbF (0.1), BkF (0.1), BaP (1), DahA (1), BghiP (0.01), and IcdP (0.1) [70]. BaP\({}_{\text{MEQ}}\) (mutagenic equivalents) were calculated as follows [72]:  
\[BaP_{MEQ}=\sum(C_{i}\;*\;TEF_{i})\]  
\[\text{(BaP}_{\text{MEQ}})_{\text{ESPAH}}=\text{[BaA]}\times 0.082+\text{[Chry]} \times 0.017+\text{[BbF]}\times 0.25+\text{[BkF]}\times 0.11+\text{[BaP]}\times 1+\text{[IcdP]}\]  
\(\times\) 0.31 + [DahA] \(\times\) 0.29 + [BghiP] \(\times\) 0.19  
The obtained values for BaP\({}_{\text{TEQ}}\) and BaP\({}_{\text{MEQ}}\) (Table 4A; Figure 10) ranged from 58 to 179 and 69 to 200, respectively, with the highest results observed at site 13, which might be caused by the pollution from the nearby small factory producing PVC windows and doors. Based on the obtained BaP\({}_{\text{TEQ}}\), the toxicity of snow cover can be represented in the following order into two groups (I--more hazardous, II--less hazardous):  
- Group I: 13 \(>\) 5 \(>\) 10 \(>\) 14 \(>\) 3 \(>\) 7 \(>\) 9;  
- Group II: 2 \(>\) 4 \(>\) 8 \(>\) 6 \(>\) 12 \(>\) 15 \(>\) 1 \(>\) 11. Figure 9: PAH sources based on COMB/PAHs vs. Flt/(Flt + Pyr) coefficients. Similarly, BaP\({}_{\text{MEQ}}\)s values can give the following group order of the samples:  
* Group I: 13 \(>\) 10 \(>\) 5 \(>\) 14 \(>\) 3 \(>\) 7 \(>\) 9;
* Group II--2 \(>\) 4 \(>\) 8 \(>\) 6 \(>\) 12 \(>\) 15 \(>\) 1 \(>\) 11. The spatial hazard of carcinogenicity and mutagenicity is shown in Figure 10. [PERSON] et al. [73] and [PERSON] et al. [74] used a level of 600 \(\upmu\)g/kg of TEQ in sediment as a threshold for environmental safety. None of the obtained values for Zawoja exceeded this limit. Nonetheless, compared to the BaP\({}_{\text{TEQ}}\) values from snow cover obtained by [PERSON] et al. [51], ranging between 0.89 and 40.62 ng/L, Zawoja's results were 2-4 times higher. The authors, however, mentioned that the data from Khabarovsk were more than two orders of magnitude lower than from the clean and polluted areas of the city of Novokuznetsk. In addition, values of BaP\({}_{\text{TEQ}}\) of Zawoja samples (Table 4A) ranged from 58 to 179 ng/L and, compared with the river waters, showed high correlation with the values obtained for the Euphrates waters, 73.4 ng/L-171.3 ng/L, which according to the authors, were recognized as elevated and alarming [75]. Furthermore, the levels of potential ecological risk produced by specific PAHs were evaluated using a risk quotient (RQ), which was calculated according to equations given by [PERSON] et al.