Potential toxic elements in groundwater and their health risk assessment in drinking water of Limpopo National Park, Gaza Province, Southern Mozambique

Concentrations of trace elements in drinking water affect its safety and acceptability for use. Potentially toxic element (PTE) contaminations are considered extremely hazardous because of toxicity, persistence, and bioaccumulative behaviour. Many areas in the Southern African Development Community are data poor and have poor accessibility. The results of our previous research identified the presence of fossil waters in southern Limpopo National Park. Groundwater and river water are the only sources of drinking water for the villages in the study area. The current study focuses on the understanding of trace element distribution and health perspectives of PTEs (Hg, U, Sr, B, and Mn) in the groundwater and surface water samples (rivers and lakes) collected within the buffer zone of the Limpopo National Park, Southern Mozambique. Two sampling campaigns (October 2016–March 2017) were carried out during the end of the wet season and the end of the dry season to analyse the differences. The results improved our knowledge of the occurrence of trace elements in drinking water in an area where water resources play a fundamental role—because of their scarcity—and where the climate is harsh. ICP-MS results provided information on concentration ranges, highlighting the exceedance of the permissible maximum limit of mercury imposed by the World Health Organization on several groundwater samples. In the buffer zone of Limpopo Park, the highest levels of risk seem to be associated with the presence of Hg and U in drinking water. The use of risk assessment markers such as non-cancer risk value (hazard quotient [HQ]) revealed the exceedance of HQ values for Hg and U. The HQ values are higher in the wet season than the dry season, and most of the exceedance has been found in groundwater. HQ values are higher in exposed children than exposed adults. The water of Lake Massingir seems to be safer than any other source, but people do not currently use it because of the distance between the lake and their villages. Proactive control and research on alternative solutions for the water needs of the population and on creation of water distribution are recommended. In the current study, drinking water was the only route of exposure that was evaluated. Therefore, it would be appropriate to investigate the concentrations of PTEs in crops, livestock, and any other potential pathways.