Heavy Metal Content in Acacia saligna and Acacia polyacantha on Slime Dams: Implications for Phytoremediation

Aims: To determine heavy metal content in A. saligna and A. polyacantha so as to ascertain their possible use in phytoremediation

Place and Duration of Study: Bindura University of Science Education, Chemistry and Biological Sciences Dept, P. Bag 1020, Bindura, Zimbabwe. The study was carried out between December 2011 and January 2013.

Methodology: Two sites which are the slime dams at a local gold mine in Bindura and a control site 10km outside the slimes were used in the study. A total of four sampling points each in the form of 5x5m quadrants were established after every 100m in transects, 700m long separately established on the control and slime dams. Soil samples at 5-10cm and 10-15cm levels as well as roots, leaves and bark from five sampled plants were collected at each sampling point. The metals content was analyzed using Atomic Absorption Spectrometry and Inductively Coupled Plasma. The bioaccumulation factor and the shoot/root quotient were computed in Microsoft excel. Analysis of Variance was carried out using SPSS and Genstat Version 16.

Results: The present study shows that A. saligna and A. polyacantha accumulate heavy metals with biological accumulation factor (BAF) value results indicating significant differences between the slimes and control sites. Both species had BAF values for nickel, copper and iron greater than one except for zinc, lead and arsenic. The shoot/root quotients showed that nickel, copper and iron are translocated to the shoots in the species as compared to zinc, lead and arsenic.

Conclusion: A. saligna and A. polyacantha showed evidence of accumulation of nickel, copper and iron and therefore may be used for phytoremediation and restoration purposes at mine slime dams