# Physico-Chemical Parameters and Health Risk Analysis of Groundwater Quality
## 2 Materials and Methods
### Groundwater Analysis
Pb was significantly correlated with Cr (\(p<0.01\)) and Ni (\(p<0.05\)), and these correlations may reflect similar sources of pollution or similar cumulative characteristics among the corresponding samples. Between Pb-Zn, Pb-Mn, Cr-Mn, Zn-Ni, and Mn-Ni were observed low positive Pearson correlations. However, no statistical correlation was found between these pairs, likely indicating the different origins of these elements. There was an inverse relationship between Pb-Cu, Cu-Cr, and Cu-Ni, which was likely due to their origins from different sources, or antagonism. Positive Pearson coefficients between metals suggest a pollution source (industrial, urban, or agriculture pollution). In addition, to verify if there is variability between groundwater samples from different areas (rural and urban), an analysis of variance (ANOVA) was carried out. According to this test, statistically significant differences were not found between samples from urban and rural areas (\(p>0.05\)). In addition, a Pearson correlation analysis was used to identify the relationship between metals concentrations and water physico-chemical parameters (pH, conductivity, total alkalinity, nitrates, nitrites, hardness, turbidity, ammonium, and chloride)--Table 6.  
Pb showed strong positive significant correlation with total alkalinity, and Cu and Zn with turbidity. In the studied groundwater samples, metals showed small positive correlations with most of the physico-chemical parameters (Pb with C, NO\({}_{3}^{-}\), d\({}_{7}\); Cu with pH, TA; Cr with C, TA, NO\({}_{3}^{-}\), d\({}_{7}\); Zn with pH. TA, NO\({}_{3}^{-}\); Mn with TA, TU and Ni with C, TA, NO\({}_{3}^{-}\), d\({}_{7}\)). For the other studied metals with physico-chemical parameters, a low negative correlation was observed. \begin{table}
\begin{tabular}{c c c c c c c c} \hline  & **Cd** & **Pb** & **Cu** & **Cr** & **Zn** & **Mn** & **Ni** & **Fe** \\ \hline Cd & 1 & & & & & & & \\ Pb & NaN & 1 & & & & & & \\ Cu & NaN & \(-0.351\) & 1 & & & & & \\ Cr & NaN & \(0.963\)** & \(-0.264\) & 1 & & & & \\ Zn & NaN & \(0.265\) & \(0.817\) & \({}^{*}\) & \(0.157\) & 1 & & & \\ Mn & NaN & \(0.360\) & \(0.736\) & \(0.292\) & \(0.889\) & \({}^{*}\) & \(1\) & & \\ Ni & NaN & \(0.900\) & \({}^{*}\) & \(-0.200\) & \(0.791\) & \(0.302\) & \(0.450\) & 1 & \\ Fe & NaN & NaN & NaN & NaN & NaN & NaN & NaN & 1 & \\ \hline \end{tabular}  
NaN (not a number) means there is a result, but it cannot be represented in the computer. ** Correlation is significant at the 0.01 level. \({}^{*}\) Correlation is significant at the 0.05 level.  
\end{table} 
Table 5: Pearson correlation coefficients of metals in groundwater samples. Chloride as the representative ion of salinity had negative correlations with all studied metals, except Ni (\(r\) = 0.01), indicating that terrestrial inputs strongly contributed to the distribution of these metals in groundwater samples. Thus, in the central area of Bangladesh, located in the south of the Asian continent, values were recorded for Fe from 52 to 19.600 \(\upmu\)g/L, for Mn from 0.04 to 4.23 \(\upmu\)g/L, for Ni from 1.1 to 18.8 \(\upmu\)g/L, for Pb from 0.02 to 28.6 \(\upmu\)g/L, and for Zn from 2 to 58 \(\upmu\)g/L [33]. Comparing these results of heavy metals in the groundwater of central Bangladesh with those of groundwater in the Dobrudja area, it can be seen that Fe, Mn, and Pb exceed the maximum permissible limits. It can also be seen that in the groundwater of the southern part of the Asian continent there are large quantities of heavy metals compared to those found in the groundwater of the southeastern part of the European continent, more precisely in the Dobrudja area of Romania. Also in Bangladesh, but this time in the western area, data on the existence of trace metals were monitored, which showed that of the six metals analyzed, namely Cu, Cd, Fe, Mn, Ni and Zn, only Cu and Zn were within the maximum allowed limits, the rest of the metals being found in much larger quantities [34].