Heavy metal contamination in water, soil and a potential vegetable garlic (Allium sativum L.) in Punjab, Pakistan

Heavy metal contamination in soil, water, and garlic (Allium sativum L.) (watered with canal, ground and sewage waters) in a semi-arid region was investigated in this study. A sub-urban area of district Khushab, Pakistan was chosen as the study site to assess the risks associated with the consumption of this vegetable supplied with three different types of water for irrigation. Sewage water had higher contents of metals and metalloids (Cu, Ni, Se, Mo, As, Fe and Zn) than in other waters. Mean metal concentrations were below the permissible values, but those of Pb and Mo exceeded their respective limits. Metal correlation for the vegetable and soil was significantly positive except for Cu. The range of bio-concentration factor varied between 0.06-20.51 mg/kg. The sewage water had the highest pollution load index. Zinc had the highest daily intake value (0.199), while Se had the lowest value (0.003). The range for health index stood between 0.261-73.44 mg/kg. Metals like Zn, Ni and Cu had enrichment factor higher than 1.0 which raised serious health concerns. It has been a routine to irrigate crops with sewage water but proper management of wastewater is required prior to its supply to the fields. Hazardous quotient (HQ) indicated alarming levels of different metals with respect to public health due to utilization of this vegetable receiving wastewater irrigation. (author)