Cadmium (Cd) and lead (Pb) concentrations effects on yields of some vegetables due to uptake from irrigation water in Ghana

Heavy metal contamination of agricultural soils from wastewater irrigation is of serious concern since it has implications on human health. Systemic health problems can develop as a result of excessive accumulation of dietary heavy metals such as cadmium (Cd), lead (Pb) and chromium (Cr) in the human body. A study was carried out at the Kwame Nkrumah University of Science and Technology (KNUST) campus in Ghana using water to which Cd and Pb had been added to irrigate cabbage, canots and lettuce. Cadmium and Pb solutions of concentrations 0, 0.05 and 0.1 mg L^-1 and 0, 30 and 50 mg L^-1, respectively were formulated and used to irrigate the crops. Plant and soil samples from the experimental fields were collected for laboratory analysis. Results showed reduction in yields of lettuce from the treatments. Cadmium treatment of lettuce with 0.05 mg L^-1 concentration of irrigation water reduced yield by 11% whilst 0.1 mg L^-1 Cd concentration of irrigation water treated lettuce yield reduced by 16%. However, there were increases of 61 and 53%, respectively in yields of carrots irrigated with water containing 0.05 and 0.1 mg L^-1 Cd in comparison with carrots irrigated with water containing 0 mg L^-1. Yields of crops irrigated with irrigation water containing Pb concentrations of 30 and 50 mg L ^-1 were reduced compared with yields from the control plots. Plant Cd and Pb concentrations increased with irrigation water concentrations significantly with p-value of Cd<0.0001 and for Pb <0.05. Cadmium concentrations for cabbage were between 0.09 and 1.11 mg kg^-1 whilst canots and lettuce had values between 0.04, 1, 0.12 and 1.02 mg kg^-1, respectively. Lead concentrations in cabbage ranged between 0.18 and 15.2 mg kg^-1, for canots and lettuce they were 0.43 to 6.24 mg kg ^-1 and 1.41 to 187 mg kg^-1, respectively.