# Physico-Chemical Parameters and Health Risk Analysis of Groundwater Quality
## 2 Materials and Methods
### Groundwater Analysis
The principle of the method for chlorides determination was chlorides precipitation with silver nitrate solution in the presence of potassium chromate as an indicator. The end point of the titration is highlighted by the appearance of the silver-chromate precipitate, colored brick-red. Metals (Cd, Pb, Cu, Cr, Zn, Mn, Ni, Fe) were determined by atomic absorption spectrometry (AAS). Atomic absorption spectrometer contrAA 700 Analytik Jena was equipped with a graphite furnace with a background correction system and cavity cathode lamp. Table 1 presents the calibration data and detection limits. Water samples are filtered and preserved by acid treatment. A volume of 20 uL of sample solution was injected into the platform graphite furnace of the atomic absorption spectrometer. The oven is electrically heated. By gradually increasing the temperature the sample is dried, pyrolyzed, and atomized. The light source emits a specific light for each analyte. When the ray of light passes through the cloud of atoms in the heated graphite furnace, light is selectively absorbed by the atoms of the analyte. The decrease in light intensity is measured with a detector at a specific wavelength. The concentration of metals in the sample was determined by comparing the absorbance of the sample with the absorbance of the calibration solutions, according to [PERSON]'s law. Chemical modifiers are used to remove its spectral non-spectral interference from a sample (matrix effects). For Cd, Cr, Cu, Fe, Mn, Zn the chemical modifier Pd/Mg (NO3)2 0.1: 0.05% was used, and for Ni and Pb, Pd (NO3)2 0.05%. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Metals** &
\begin{tabular}{c} **The Range** \\ \(\mu\)g/L \\ \end{tabular} & **R2** & **LOQ** \\ \hline Cd & 0.4–4 & 0.9913 & 0.00041 \\ Cr & 2–20 & 0.9902 & 0.00206 \\ Cu & 3–30 & 0.9902 & 0.00310 \\ Fe & 3–30 & 0.9930 & 0.1183 \\ Mn & 1.5–15 & 0.9978 & 0.00151 \\ Ni & 7–70 & 0.9940 & 0.00708 \\ Pb & 10–100 & 0.9946 & 0.01002 \\ Zn & 0.5–5 & 0.9924 & 0.1076 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Calibration data and quantification limits. The permanent alkalinity had the same value for all six groundwater samples in the Dobrudja region (0.000 mmol/L), while the values for total alkalinity fluctuated--the highest value being recorded for the water from Palazu Mare (13.0 mmol/L) and the lowest for the water in the rural district of Casimcea (8.0 mmol/L). The concentration of nitrate contained in water seems to be from the high agricultural waste and sewage contamination. Such an increase may be due to rapid decomposition of organic matter. When the dead organic matter decomposes in water, it forms complex proteins, which are converted into nitrogenous organic matter and finally to nitrate by bacterial activity. The highest level of nitrates was found in the waters of Casimcea (532 mg/L), and the lowest in Lumina (0.132 mg/L). For nitrites, the highest level was highlighted in the groundwater in Casimcea (0.245 mg/L), and the lowest level in Lumina (0.002 mg/L). The highest value of hardness (95.9) was found in the waters of Casimcea, while the lowest value was identified in the waters of Lumina (21.2). The studied waters thus fall into the category of hard waters (those from Lumina and Corbu) and very hard waters, with hardness values over 30 degrees German hardness. Higher turbidity affects life indirectly by cutting the light utilized by phytoplankton growth. It should be noted that the water in Lumina had the highest value of turbidity (0.75 UTF). The lowest value could be observed for the waters in Constanta (0.013 UTF). At all sites turbidity is low (Table 2), because there is no exploitation activity in the area. Ammonium is an indicator parameter of recent organic pollution. Its sudden increase indicates the intervention of a pollutant of either natural or artificial origin. The ammonium parameter registers the highest value in Corbu (0.075 mg/L), and the lowest value is found simultaneously in two areas: Palazu Mare and Palas (0.001 mg/L).