Occurrence and Seasonal Variations of Lead Concentrations in River Water and Edible Vegetables Grown along Morogoro River Bank

Abstract

Urban vegetable farming is popular in Tanzania and other countries partly due to readily available market and reliable transport to reach consumers. River banks are usually used to grow such vegetables due to closer proximity to water and whenever necessary use such water for irrigation. However in urban settings river water pollution by toxic heavy metals and subsequent accumulation of the metals in nearby grown vegetables has been reported as among major sources of exposure to humans and animals. Heavy metals, including lead (Pb) have many health effects to human and animals ranging from acute to chronic illnesses. This study was conducted to assess the occurrence of lead in Morogoro river and in edible vegetables (Amaranthus retroflexus) grown along the river bank. Water and vegetable samples collected during dry and rainy seasons were prepared and analysed for occurrence and levels of lead using Atomic Absorption Spectrometry (AAS). It was found that concentration of Lead in the water and vegetable samples were up to 0.95 mg/L, and 0.026 mg/Kg respectively. It was also found that 77% of the water samples and 28% of the vegetable samples had lead levels above the WHO recommendations. The frequency and levels of lead occurrence varied with topographical, diurnal and seasonal characteristics of sample collection. The results of this study raise concerns on the use of water for human and animal consumption from rivers which run across urban areas and call for further studies to investigate for any health consequences to consumers