This study was carried out in the Massissia district, located south of the city of Brazzaville. This district covers an area of 80.45 km². It is bounded to the north by the district of Goma Tsé-Tsé, to the south by the Makélékélé district, to the west by the Djoué and to the east by the Congo River. In order to solve their water problem, these populations use water from springs, boreholes and wells for their daily tasks.

Figure 1 illustrates the study area (Massissia district).

The sites that were selected for this study are located in highly populated areas, and are therefore very popular. Some information on the sampling point are given in Table 1.

Figure 2 represents the images of differents sampling points.

This study was carried out in the period from January to July 2021 on six sampling points including two wells, two springs and two boreholes and all the water samples were taken respectively in January, April and July. The following parameters were measured in situ: pH, temperature, conductivity.

The well water was sampled using a container used by the users, the water in the container was then put back into a 1.5 L bottle then placed in a bag and then transported to the laboratory for analyzes [8] .

All the selected springs being equipped; the sample was taken after sterilization of the water outlet tap with alcohol. Water flowing from the tap was then placed in 1.5 L bottles.

At the boreholes, water was taken from the tap after letting the water run for a five minutes and then placed in 1.5 L bottles.

The water samples intended for the microbiological analyzes were placed in sterilized jars then kept in a cooler containing ice.

Color and turbidity were provided using the Lamotte spectrophotometer. The pH of the waters was determined using a HANNA HI 83141 pH meter, the total hardness by titration using EDTA, the determination of conductivity and TDS was made at using an ADWA AD31/8000 conductivity meter, bicarbonate, alkalinity, nitrate, magnesium, chloride, calcium, phosphate, sulphate, potassium, manganese, nickel, zinc, lead, and chromium ions using a Lamotte spectrophotometer [9] [10] .

For the microbiological analyzes, the prepared media were stored between 2 and 8˚C and using 0.45 μm filter membranes. The two procedures used to detect yeasts and molds are M-Green Agar and Mannitol Salt Agar [11] .

After preparation of the culture media, inoculation and reading made it possible to count the colonies of bacteria.

Three water samples were taken at each location (spring, well and borehole) to carry out physicochemical and microbiological analyzes. Figures 3-10 give in the form of histogram the average of the parameters determined for each type of water.

The groundwater in the present study is around acidity. Average pH values below 7 are observed in all the water points except in point MP1.

The pH values of the samplings points MP2, MF1, MF2, MS1 and MS2 are between 5.80 and 6.21, these results are in line with those of ZOULGAMI [12] who found pH values between 5.7 and 7.87 for groundwater in TOGO. The distribution of the pH in the waters of the Massissia sector would come from the decomposition of plant organic matter, with the production of CO₂ in the first layers of the soil, which corroborates with the work of MBILOU et al. [13] .

The average conductivity values vary between 200 µS/cm and 300 µS/cm at the wells and boreholes, while they are above 300 µS/cm at the springs. The conductivity being proportional to the quantity of mineral salts, it can be deduced that the springs MS1 and MS2 have an accentuated mineralization and that the rest of the water points have a moderately accentuated mineralization. These results are different from those observed by NGOUALA [14] , the latter observed relatively lower values which oscillate between 16.33 and 47.17 µS/cm.

The high conductivities obtained during this study may be linked to anthropogenic activities which are diversified and intensified in the study area, and cause water mineralization by surface inputs.

Silica levels are high in water points and are generally higher than the WHO standard (12 mg/L). These results are consistent with those obtained by MBILOU et al. [15] , who worked on the physicochemical characterization of groundwater in the southern zone of Brazzaville. The silica concentrations revealed by the work of the latter in the part of Massissia presented values higher than the WHO standard, he indicates that this fact would probably be linked to the presence of silicate minerals constituting the groundwater.

The TDS values varying from 119 to 197 mg/L. The high concentration of TDS in all the sampling points indicates a mineralization which is still within the standard. These values are in agreement with the WHO standard and in disagreement with the results observed by MUSUMBA et al. [16] , who found values include between 88 and 160 mg/L in groundwater of Wakiso district, Uganda.

The very low values of turbidity in all the samples demonstrated that, although having taken the samples in the rainy season, there was no infiltration or percolation and therefore, that the soils probably have a permeability quite important.

Iron and zinc are absent in all samples. Potassium and calcium are present at levels adapted to the WHO standard at all the sampling points. However, we note a Cadmium content that exceeds the standard with average values of 0.21 mg/L in the wells water, 0.47 mg/L in the springs water and 0.24 mg/L in the borehole water. The presence of nigh concentration of Cadmium constitutes a risk for consumption.

The results of the microbiological analyses are given in Table 2.

The microbiological analyzes revealed:

- The presence of yeasts and molds in all samples. These elements not being naturally present in the water, would suggest contamination of anthropogenic origin. These results are consistent with those obtained by KANOHIN et al. [17] and who claim that their presence is an essential and undeniable indicator of significant water contamination.

- The presence of total coliforms, in a content greater than the 0 CFU/100 mL standard, indicator of faecal contamination; these results corroborate those observed by El Ouali Lalami et al. [18] and is based on the hypothesis that total coliform contamination is probably linked to multiple discharges of wastewater loaded with abiotic pollutants;

- The presence of staphylococci; the same observation was made by Palamuleni et al. [19] starting from a standard of 0 CFU/100 mL. Its presence relates to contamination linked to anthropogenic activities (discharge of waste water);

- The presence of E. Coli only suggests contamination when they are present in a quantity greater than the standard used. Springs MS1 and MS2 do not reveal any presence of E. Coli, which does not mean that they are not contaminated.

- The presence of Salmonella and Shigella once again confirms that these waters are unfit for consumption; this observation is consistent with that of NOLA et al. [20] , with a percentage of Salmonella evaluated at 17% in the rainy season and 8% in the dry season on groundwater.