The area of interest is the Central Plateau region, located at 2˚15' and 0˚20' west longitude and 11˚45' and 13˚00' north latitude. The study area belongs to the Northern Sudan climatic zone, which is characterized by an alternating dry season from mid-October to mid-May and a rainy season from mid-May to mid-October. The average annual rainfall in the area varies between 650 mm and 800 mm and is characterized by a low spatio-temporal distribution. The average annual temperature in this zone is about 28.5˚C, with mean and absolute minima of 16˚C in December and January and mean and absolute maxima of 39˚C in March and April. The warmest months are March, April, and May, while the coldest months are December, January, and February.

The Central Plateau region is part of the geology of the West African Craton. The West African Craton is a magnet for mining industries and small-scale artisanal gold miners because of its numerous gold deposits. With respect to the geology of the study area, the bedrock is mainly leucocratic to sub leucocratic granite with biotite and sometimes muscovite. Banded and foliated granodiorite, tonalite and quartz diorite are also found, with significant quartz vein crosscutting (Castaing et al. 2003) [14] Figure 1.

The study was conducted in the rural commune of Méguet, located 26 km north of the commune of Zorgho, capital of Ganzourgou Province in the Central Plateau region, and about 100 km from the capital city of Ouagadougou, Burkina Faso. This rural commune which is the subject of our study has leached tropical ferruginous soils.

During this phase surface water (dams and site), groundwater (boreholes) and mine sediments were sampled (Figure 2). During this phase, physical parameters such as temperature, hydrogen potential (pH) and electrical conductivity were measured in situ using a multi-parameter instrument. To obtain samples ready for laboratory analysis, the following steps are followed preparation of sampling sheets and labels to be attached to the bottles; use of latex gloves to avoid contamination of the samples; use of 1 liter polyethylene bottles previously

washed in distilled water, including two (02) per sampling point, one for heavy metals analysis and the other for free cyanide; use one bag to collect 1 kg of mining sediment from each site and another bag for 1 kg of control soil at a depth of 30 to 40 cm as a neutral sample; For heavy metals and cyanide analysis, rinse the water points for a few minutes to remove supernatants and obtain representative samples; thoroughly rinse the bottles at least three times with the water to be analyzed prior to sampling while wearing latex gloves; empty the bottle with the opening facing down before immersing it vertically in the water. When it’s well submerged (about 30 cm), tilt it about 45˚, fill it halfway and add the stabilizing additive. Immediately rinse the cork and carefully close the bottle; use nitric acid (NHO₃, 1 ml) as a stabilizing additive in bottles intended for heavy metal analysis and sodium hydroxide (NaOH) as a stabilizing additive for cyanide analysis; use an airtight cool box with a cold preservative (“boxe glace”) to keep the samples at a temperature below 4˚C suitable for laboratory analysis; return the samples to the laboratory within 24 hours.

Physical parameters were analyzed in situ to study their correlation with heavy metal concentration. Physical parameters such as hydrogen potential (pH), temperature (˚C) and electrical conductivity (μS/cm) were sampled in the field using a branded multimeter. Sampling points were geolocated and coded by sample. Samples included wash sediments, drilling water, wash water, dam water and control soil.

Heavy metals such as Ag, As, Cd, Co, Cr, Cu, Fe, Hg, Mn, Ni, Pb, Ti, and Zn were determined by the Inclusive Coupled Plasma (ICP) method. Cyanide was analyzed using a titroprocessor equipped with a CN-specific electrode. However, the values obtained were subjected to statistical analysis. All statistical analyses were performed using Microsoft Excel 2013 for graphical presentation.

All physical parameters of the water measured in situ are summarized in Table 1.

A correlation graph (Figure 3) between the three parameters (pH, electrical conductivity and temperature) shows that the borehole water from Site 2 has the highest relative value for electrical conductivity, with a lower pH near of an average temperature of 29˚C.

A total of 14 samples were analyzed for heavy metals (see Table 2) and another

seven samples were analyzed for free cyanide (CN) (see Table 3). The distribution and comparison of the elemental concentrations present in the samples

from the two sites, as well as from the dams, boreholes and control soil, will allow us to determine their origin (natural or anthropogenic) and to conclude whether they are contaminated. In this case, the hypothesis of contamination by gold panning would be confirmed, in accordance with the World Health Organization (WHO) [15] standards in force in Burkina Faso.

Analysis of in situ physical parameters revealed that the waters analyzed are basic to slightly basic (6.97 < pH < 8.1). This is a favorable environment for chemical and biochemical reactions. It is also a determining factor for the growth of micro-organisms living in the water, specially bacteria according to Roudier [16] , since most of them prefer neutral or slightly alkaline pH values between 6.5 and 8.5 [17] . For this study, all samples had a pH well within the WHO standards (6.5 < pH < 8.5).

Temperature ranged from 24.6˚C to 31.6˚C. Between 10˚C and 30˚C, temperature has a negligible effect on metal mobility [18] . However, in a mining environment, an average temperature of 30.3˚C could affect acid mine drainage (AMD), which is the most significant environmental problem in the extractive industry [18] .

The different electrical conductivity measurements (124 < EC < 543 μS/cm) indicate a low mineralization of the water in the analyzed samples. This low mineralization could be explained by the fact that the water at the sites studied is only slightly charged.

Mining mineralized veins releases more particles into the water. In fact, the waters of the study area are loaded with sediments from gold panning and farmland erosion as explained by Mboudou et al. [19] , which promote the development of microorganisms and other aquatic plants.

Analysis of the samples revealed metal concentrations well above the normal range [15] , especially in the solid samples, i.e. the control soil and the ore washing sediments.

These unusually high concentrations in the solid samples prove that trace metals have a natural origin in the environment and are the signature of existing geological formations. They are present in small quantities in rocks [20] . This natural presence, under the effect of transport agents such as water erosion by runoff, wind and infiltration, most often favored by agriculture and gold panning activities, could lead to a very high mobility of these elements towards water points (streams, rivers, dams, boulders and boreholes) for consumption or gardening. This abnormal distribution could contaminate the entire food chain, causing health problems for humans and wildlife, as well as the decline or disappearance of certain plant species and the impoverishment of the land.

The concentration of free cyanide (CN) monitored in the various samples was zero. This may be due to the fact that mining regulations prohibit its use in gold panning. In addition, we did not have access to certain ore processing areas that were considered highly suspect. On the other hand, the absence of cadmium (Cd) and cobalt (Co) concentrations in the various samples may be due to the nature of the mined rock, which is poor in these elements.

The results obtained from the liquid samples show low or very low levels of certain heavy metals. Mercury (Hg) and iron (Fe) were found in all liquid samples, with concentrations mostly above WHO recommended standards. These two elements are found in very high concentrations, especially in surface water and ore washing water at the two operating gold panning sites. Sulfur and iron are present in sphalerite (ZnS), chalcopyrite (CuFeS₂), galena (PbS) and pyrite (FeS₂), whose alteration is thought to be the reason for their presence in the environment [21] . The mineralization in the gold veins comes from quartz veins, which would support the high probability of the presence of sulfur according to Miquel, [22] . In addition, studies have shown that iron content is generally high in West Africa due to leaching from lateritic terrains [23] . Manganese generally accompanies iron in rocks and water. Not surprisingly, manganese concentrations in groundwater are on average 10 times lower than iron concentrations [24] . In our case, the concentrations of manganese are significantly lower than those of iron. The presence of manganese in water is primarily an organoleptic (metallic taste) and aesthetic (black color) nuisance. This nuisance can be perceived by the consumer at a concentration of 0.03 mg/L [22] . The mercury is therefore partly due to the geology of the area, although the high concentrations observed are directly related to its use in amalgamation during ore concentration.

The content of As, Cr, Ni, Mn, Cu, Pb and Zn in some liquid samples is below the WHO standards for Burkina Faso. This could be justified by the geological nature of these environments, which are probably low in these elements. High levels of trace metals in surface waters analyzed in a mining context are generally attributed to mining activities. In fact, for Mengnjo [25] , the substances found in the surface waters of the region are derived from the chemical alteration of mineralized bedrock and gold panning, as surface water is the main transport route. All of the chemical elements monitored occur naturally in rocks, and their presence in surface water is also normal. They are also present in the groundwater surrounding the sites, in varying concentrations in the places where monitoring is required. In fact, given the interconnectedness of these waters, it would not be out of the question to find levels of certain chemical elements that are not recommended for drinking in some wells used by local residents.

Based on the results of our field surveys and chemical analyses, which revealed water concentrations that generally deviated from natural levels of heavy metals, we can confirm our initial hypothesis that gold panning contributes to water pollution. This study allowed us to determine the extent of the elements analyzed and to specify the elements with which these waters are polluted. Among the elements analyzed, we found that Hg, Fe and, to a lesser extent, Pb and As, are at the origin of the pollution.

In short, metals are naturally present in trace amounts in the human body. They are essential for the proper functioning of our organism. For example, we have traces of calcium, potassium, iron, zinc and magnesium.

On the other hand, they can be toxic when present in excessive amounts. For example, cadmium damages the liver; lead causes lead poisoning, which is particularly serious in children; mercury is neurotoxic [22] .

Chronic exposure to TMEs often results in fatigue, headaches, sleep disturbances, difficulty concentrating, mental disorders, and digestive problems. TMEs appear to be associated with the development of serious diseases such as multiple sclerosis and neurodegenerative diseases such as Alzheimer’s and Parkinson’s.

TME damage the respiratory and digestive systems and can cause kidney failure. Heavy metal contamination can have both short- and long-term side effects, damaging systems and organs that cannot always be completely reversed by treatment in cases of prolonged overexposure.