Assessment of physico-chemical qualities and heavy metal concentrations of Umgeni and Umdloti Rivers in Durban, South Africa

Abstract

We assessed the effects of seasonal dynamics on the physico-chemical qualities and heavy metals concentrations of the Umgeni and Umdloti Rivers in Durban, South Africa. Water samples were taken from nine different sampling points and analysed for the following parameters; temperature, pH, turbidity, electrical conductivity (EC), biological oxygen demand (BOD₅), chemical oxygen demand (COD), phosphate (PO₄ ²⁻), nitrate (NO₃ ²⁻), ammonium (NH₄ ⁺), sulphate (SO₄ ²⁻), lead (Pb²⁺), mercury (Hg²⁺), cadmium (Cd²⁺), aluminium (Al³⁺), and copper (Cu²⁺) using standard methods. The data showed variations it terms of the seasonal fluctuations and sampling regime as follows: temperature 12–26.5 °C; pH 5.96–8.45; turbidity 0.53–18.8 NTU; EC 15.8–5180 mS m⁻¹; BOD₅ 0.60–7.32 mg L⁻¹; COD 10.5–72.9 mg L⁻¹; PO₄ ²⁻ < 500–2,460 μg L⁻¹; NO₃ ²⁻ <0.05–4.21 mg L⁻¹; NH₄ ⁺ < 0.5–1.22 mg L⁻¹; SO₄ ²⁻ 3.90–2,762 mg L⁻¹; Pb²⁺ 0.023–0.135 mg L⁻¹; Hg²⁺ 0.0122–0.1231 mg L⁻¹ Cd²⁺ 0.068–0.416 mg L⁻¹; Al³⁺ 0.037–1.875 mg L⁻¹, and Cu²⁺0.006–0.144 mg L⁻¹. The concentrations of most of the investigated parameters exceeded the recommended limit of the South African Guidelines and World Health Organization tolerance limits for freshwater quality. We conclude that these water bodies are potentially hazardous to public health and this highlights the need for implementation of improved management strategies of these river catchments for continued sustainability.