## 3 Results
### Hydrometeorological Conditions in the Catchment of the River Swierszcz
#### 3.2.3 Analysis of Selected Chemical Indicators
The limit was also exceeded once in rainwater sampled at point P2. \begin{table}
\begin{tabular}{c c c c c c c c c c} \hline \hline
**Point** & **Valid N** & **Mean** & **Median** & **Min** & **Max** & **Std. Dev.** & **Coef. Var.** & **Var.** & **Covariance * (\%)** \\ \hline \multicolumn{10}{c}{pH **\({}^{**}\)**} \\ P1 & 10 & 6.90 & 7.32 & 6.2 & 7.9 & 0.50 & 7.25 & Low & 90 \\ P2 & 10 & 6.79 & 7.50 & 6.1 & 7.9 & 0.60 & 8.84 & Low & 80 \\ P3 & 10 & 7.26 & 7.45 & 6.8 & 7.8 & 0.31 & 4.27 & Low & 100 \\ P4-P7 & 4 & 7.69 & 7.70 & 7.6 & 7.8 & 0.08 & 1.041 & Low & 100 \\ \hline \multicolumn{10}{c}{Ammonium ion (mg/L)} \\ P1 & 10 & 0.098 & 0.05 & 0.003 & 0.42 & 0.13 & 129.9 & Very high & 100 \\ P2 & 10 & 0.940 & 0.80 & 0.06 & 3.72 & 1.08 & 114.6 & Very high & 40 \\ P3 & 10 & 0.146 & 0.15 & 0.049 & 0.36 & 0.10 & 66.9 & High & 100 \\ P4-P7 & 4 & 0.011 & 0.01 & 0.008 & 0.012 & 0.00 & 17.6 & Low & 100 \\ \hline \multicolumn{10}{c}{Nitrates (mg/L)} \\ P1 & 10 & 2.31 & 2.37 & 0.73 & 3.72 & 1.14 & 49.3 & High & 100 \\ P2 & 10 & 1.68 & 1.53 & 0.14 & 4.25 & 1.31 & 78.0 & High & 100 \\ P3 & 10 & 1.10 & 0.975 & 0.37 & 2.4 & 0.53 & 48.4 & High & 100 \\ P4-P7 & 4 & 6.97 & 6.49 & 1.59 & 13.3 & 4.82 & 69.1 & High & 100 \\ \hline \multicolumn{10}{c}{Nitrites (mg/L)} \\ P1 & 10 & 0.010 & 0.003 & 0.0002 & 0.056 & 0.02 & 171.1 & Extremely & 100 \\  & & & & & & & & & \\ P2 & 10 & 0.151 & 0.024 & 0.0023 & 1.34 & 0.42 & 276.2 & 199 & 90 \\ P3 & 10 & 0.019 & 0.018 & 0.0038 & 0.062 & 0.02 & 87.8 & High & 100 \\ P4-P7 & 4 & 0.00045 & 0.00045 & 0.0002 & 0.0007 & 0.00 & 64.2 & High & 100 \\ \hline \multicolumn{10}{c}{Manganese concentration (mg/L)} \\ P1 & 10 & 0.005 & 0.004 & 0.0002 & 0.011 & 0.00 & 81.2 & High & 100 \\ P2 & 10 & 0.021 & 0.010 & 0.001 & 0.084 & 0.03 & 131.5 & Very high & 80 \\ P3 & 10 & 0.101 & 0.088 & 0.0113 & 0.21 & 0.06 & 61.5 & High & 20 \\ P4-P7 & 4 & 0.012 & 0.01 & 0.006 & 0.022 & 0.01 & 58.1 & High & 100 \\ \hline \multicolumn{10}{c}{Total iron concentration (mg/L)} \\ P1 & 10 & 0.0358 & 0.031 & 0.013 & 0.066 & 0.02 & 54.5 & High & 100 \\ P2 & 10 & 0.0955 & 0.021 & 0.003 & 0.670 & 0.21 & 215.1 & Extremely & 100 \\ P3 & 10 & 0.599 & 0.541 & 0.299 & 0.969 & 0.24 & 40.4 & High & 0 \\ P4-P7 & 4 & 0.0325 & 0.033 & 0.003 & 0.062 & 0.03 & 99.6 & High & 100 \\ \hline \multicolumn{10}{c}{Chlorides (mg/L)} \\ P1 & 10 & 1.020 & 1.025 & 0.134 & 2.18 & 0.58 & 56.757 & High & 100 \\ P2 & 10 & 1.339 & 0.73 & 0.13 & 3.06 & 1.16 & 86.643 & High & 100 \\ P3 & 10 & 1.684 & 1.75 & 0.201 & 3.11 & 1.06 & 63.205 & High & 100 \\ P4-P7 & 4 & 3.93 & 3.285 & 3.15 & 6 & 1.38 & 35.18 & Moderate & 100 \\ \hline \multicolumn{10}{c}{Total hardness CaCO\({}_{3}\) (mg/L)} \\ P1 & 10 & 14.59 & 12.1 & 3.37 & 34 & 11.35 & 77.792 & High & 0 \\ P2 & 10 & 8.16 & 7.595 & 2.3 & 14 & 4.14 & 50.675 & High & 0 \\ P3 & 10 & 126.1 & 128.5 & 103 & 139 & 11.28 & 8.944 & Low & 100 \\ P4-P7 & 4 & 194.75 & 198.5 & 157 & 225 & 29.89 & 15.35 & Low & 100 \\ \hline \hline \end{tabular} \({}^{*}\)Compliance with the drinking water standard. ** During the calculations of mean pH, the individual pH values were converted to the corresponding hydrogen ion activity.  
\end{table} 
Table 5: Descriptive statistics of the tested chemical parameters of rainwater compared with those of flowing water and groundwater. In the case of chlorides, the drinking water standard of 250 mg/L was not exceeded in any of the measurement points (Figure 10g). The lowest content of chlorides was found in rainwater (P1 and P2) and the highest was found in groundwater (P4-P7). Figure 10: Boxplots of the chemical parameters of the tested water groups. A comparison of the quality of rainwater (P1, P2), river water (P3) and water from the deep wells (P4–P7) with the corresponding drinking water standards. \({}^{\text{ab}}\) Distributions of results in the groups not containing the same letter differed significantly at \(\alpha=0.05\) (Kruskal–Wallis test).