Assessment of Heavy Metal Accumulation in Wastewater-Receiving Soil-Exotic and Indigenous Vegetable Systems and Its Potential Health Risks: A Case Study from Blantyre, Malawi
Chimwemwe Chiutula, Andrew G. Mtewa, Amon Abraham, Richard Lizwe Steven Mvula, Alfred Maluwa, Fasil Ejigu Eregno, John Njalam'mano
International Journal of Environmental Research and Public Health
Urban Farm DB summary
At the Soche Wastewater Treatment Plant in Blantyre, Malawi (built in the 1950s, current design flow 4,100 m³/day), whose effluent irrigates nearby gardens, researchers measured heavy metals by atomic absorption spectrophotometry in effluent, soil and six vegetables (three exotic Brassica varieties plus indigenous pumpkin, sweet-potato and amaranth leaves). Soil zinc reached 56.4 ± 0.5 mg/kg against a WHO limit of 36 mg/kg; vegetable stems reached 4.65 mg/kg chromium (limit 2.3) and 4.09 mg/kg lead (limit 0.3), and leaves 0.31 mg/kg cadmium (limit 0.2). Health risk indices peaked at 92.28, far above the safe threshold of 1. Limitations: sampling at a single time point (November) with no seasonal variation, and total-element rather than speciation analysis.