Assessment of Surface Water Contamination by Heavy Metals Due to Agricultural Practices in the Northern Part of Burkina Faso

Aims: The purpose of this study was to assess the status of the heavy metals As, Cd, Pb, Mn and Zn in the surface water of the Sub-catchment Barrage of Tougou for which water comes mainly from agricultural activities.

Place and Duration of Study: A total of 73 water samples were taken at the inflow of the water body and at several points located on the water body, from August to October 2019.

Methodology: Water samples were characterized for temperature, pH, electrical conductivity (EC), sulfate (SO42-), nitrate (NO3-) and phosphate (PO43-). Heavy metals were analyzed using a microwave plasma atomic emission spectrometer (MP-AES), Agilent Model 4210.

Results: The EC range was between 27.45 and 53.90 µS/cm with an average pH of 6.4. Nitrate (NO3-) was the most abundant anion in the water (39.70 mg / L) and phosphates (PO43-) were present in very small quantities (0.34 mg / L). The results showed very low concentrations of Pb and Cd, below 5 µg / L and below 2 µg / L, respectively. The concentrations of As, Mn and Zn in the water were 2.8 µg / L, 13.2 µg / L and 9.8 µg / L, respectively. Agricultural practices do not have a significant effect on surface waters. The concentrations of heavy metals analyzed in the water were lower than the standards established by the World Health Organization for drinking water quality.

Conclusion: This information, certainly important, does not allow us to conclude on the risk of the consumption of this water on human health. Further studies should be conducted on this water body to evaluate the potential risk for public health and to examine the concentrations of heavy metals in the sediments, because it is known that sediments have a high absorption capacity for heavy metals and are then considered the main target for water purification related to heavy metals.