Assessment of trace element contamination in the soil, Kikuyu grass (Pennisetum clandestinum), and local sports fields, their human health risk and environmental impacts in Pietermaritzburg, South Africa

This study examined the seasonal variation of trace elements (B, Ba, Cr, Pb, Sb, Se, Zn) in soil and Kikuyu grass (Pennisetum clandestinum) around the Darvill Wastewater Treatment Works in Pietermaritzburg, South Africa. Twenty sites were sampled during wet and dry seasons and compared with control areas, Pietermaritzburg (PMB), Dumabezwe, and Mqulela sports fields. The samples were analysed using inductively coupled plasma optical emission spectrometry (ICP-OES) for trace element concentrations. The results showed that trace element concentrations were significantly elevated near the Darvill Wastewater Treatment Works, especially during the dry season. Cr and Se had the highest soil levels, 1978 mg/kg and 1169 mg/kg, respectively. Only Cr showed substantial concentration in the Kikuyu grass tissue (957 mg/kg). The study evaluated the Kikuyu grass for soil remediation and trace element recovery; Cr (1.3) and Se (1.1) showed minimal bioaccumulation ability. Cr and Pb posed health risks via ingestion (hazard quotient > 1), particularly for children. Cr also showed the highest cancer risk, with total cancer risk values exceeding 1 × 10⁻⁴, and Zn posed minimal health risks. Geo accumulation index (I_geo) values showed high pollution from Cr (I_geo > 5), and moderate from Pb and Zn. Enrichment factor (EF) values for Cr and Zn (EF > 1.5) indicated anthropogenic sources; Pb (EF < 1.5) suggested a natural origin. Correlation and Pearson correlation analysis linked trace elements to sewage sludge application. The sports fields showed low trace element concentrations, suggesting minimal risk of cross-contamination during grass transfer and reduced trace element content in regrown grass.