Full Length Research Paper

The effect of single and mixed treatments of lead and cadmium on soil bioavailability and yield of Brassica napus irrigated with sewage effluent: A potential human risk

Chimbira C. and Moyo D. Z.*

Department of Biological Sciences, Midlands State University, P. Bag 9055, Gweru, Zimbabwe.

*Corresponding author. E-mail: moyodz@msu.ac.zw. Tel: 263-054-260575, Fax: 263-054-260233.

Accepted 15 February, 2009

   Abstract

The effect of single and mixed treatments of Lead (Pb) and Cadmium (Cb) on soil bioavailability and uptake by Brassica napus was investigated in green house using soil from Golden Ridge Estate and wastewater from Pakamisa Sewage Treatment Plant, Gweru, Zimbabwe. Pb and Cd had significant effects on metal soil bioavailability and yield in single treatments. Soil bioavailable Pb in mixed treatments significantly correlated positively with uptake by B. napus.  Yield was significantly correlated negatively with soil bioavailable Pb and Cd as well as metal uptake. Soil bioavailable Pb accounted for 49.2% (single treatment) and 6.1 % (mixed treatment) of the variation in B. napus yield. Pb uptake accounted for 4.63% (single treatments) and 88.77% (mixed treatments) of the variation in yield. Cd accounted for 0.38% (single treatment) and 7.98% (mixed treatments) of the variation in yield.  Findings of this study indicate that B. napus grown in Golden Ridge Estate soil and irrigated with wastewater from Pakamisa Sewage Treatment Plant accumulates Pb and Cd to above recommended maximum limits for human consumption and is not fit for human consumption.

Key words: Lead, cadmium, soil bioavailability, Brassica napus.