Phytoextraction of Heavy Metals and Risk Associated with Vegetables Grown from Soil Irrigated with Refinery Wastewater

Abstract

With increase in anthropogenic activities, Heavy metal pollution contamination of vegetables is inevitable as such become a course for concern due to food safety issues and potential health risk. This is aimed at evaluating the phytoextraction efficiency of some vegetables and potential health resulting from the consumption of vegetables that grown in agricultural soil irrigated with Refinery wastewater. Wastewater was collected from effluent point of Kaduna Refining and Petrochemical Company from October, 2016 to February, 2018. The wastewater was analyzed for the presence of heavy (Cd+2, Hg+2, Ag+2 and Pb+2, Cr+3) before use for irrigation. Soil samples were collected from a farm located in Rigasa, Igabi Local Governsment of Kaduna State. The soil samples were digested and analyse for heavy metal (Cd+2, Hg+2, Ag+2 and Pb+2, Cr+3) and physico-chemical parameter before and after the wastewater is used for irrigation and treatment process. The seeds of the vegetables were sow in the botanical garden of Biological Sciences Department of Kaduna State University. The sow seeds were constantly irrigated by a refinery wastewater for throughout the period of the research. After germination the plants were harvester and separated into root/rhiziome and shoot, the root/rhiziome and shoot are digested and heavy metals analysis is done using AAS. Bioconcentration factor, Biotranslocation factor, Daily intake of metal (DIM) and Health risk index (HRI) were calculated. The result obtained show The accumulation trend in the vegetable for Cd and Hg is Solanum melongena, Cucumis sativa, Phasaelus vulgaris, Spinacia Oleracea, Allium cepa, Lactuca sativa, Daucas carota, Lycopersican esculentum, Pipper nigrum. The result obtained also show high DIM and HRI value by all the vegetables that are above FAO/WHO recommended limit for the heavy metals. These researches thereby discourage the use of refinery wastewater in irrigation farming of vegetables. It also recommends the need to stop all vegetable farming activities within the bark of Romi stream since refinery wastewater is constantly been released into the stream.