Hydrochemical properties and heavy metal concentrations (ecological and human risk) of lake Rukwa
Azaria Stephano Lameck, Omar Saeed, Phenson Nsima Justine, Daniel Mwakagile, Peto Akos, Emil Boros
Abstract
This study examined lake Rukwa's hydrochemical characteristics and heavy metal levels (ecological and health hazards). Results showed average pH (8.83-8.95), EC (1470-1572.22 µS/cm), and TDS (1053.04 to 1262.63 Mg/l). The findings reveal that lake Rukwa has Na-K-HCO3 water chemical type. Gibb's diagram revealed that rock weathering and evaporation regulate water's chemical composition. The calcite and sepiolite precipitation enriches the water with Na-CO3-SO4-Cl. The study suggests silicate mineral weathering, rock-water interactions, direct ion exchange, and secondary mineral precipitation govern the geochemical evolution of lake Rukwa. The results revealed that 30% of samples had moderate ecological risk (30 < RI < 60), whereas 70% had severe risk (60 < RI < 120). The oral hazard quotient (HQ) values for lead (Pb) in children were significantly higher (HQ > 1) at all locations, indicating a potential health risk. However, the dermal HQ values were found to be within acceptable levels. Most sites had acceptable Hazard Index (HI) values, except for Pb in children and adults. In Monte Carlo simulations, heavy metal HQ values were below standard limits, except for oral Pb exposure, which exceeded 1 for adults (7.29E-04) and children (2.79E-03). The average CR values for oral and dermal lead in adults (7.29E-04, 3.47E-04) and children (2.79E-03, 1.02E-03) exceeded 1.0E-04, suggesting carcinogenic potential. These findings highlight significant oral and dermal carcinogenic hazards from Pb exposure to lake Rukwa and the necessity for effective comprehensive measures to mitigate these risks.