ABSTRACT
In recent years, much effort has been concentrated on screening a variety of hyperaccumulators, e.g. Sedum alfredii are hyperaccumulators of Zn (Yang et al. 2002), Pteris vittata and Pteris cretica for As (Chen et al. 2002), Rapeseed (Su & Huang 2002), Viola baoshanensis (Liu et al. 2003), Solanum nigrum L. and Boehmeria nivea (Ramie) for Cd, and Phytolacca americana for Mn (Xue et al. 2003). Having characteristics of hyperaccumulator, Solanum nigrum L. has strong tolerance in single
1 INTRODUCTION
Soil contamination is largely due to natural weathering of rocks, soils, volcanic eruptions, agriculture and forestry, various industrial activities e.g. ore beneficiation, metal smelting, waste disposal, fossil fuel combustion that led heavy metal migration into the water course and soil (Hutchinson & Meema 1987, Cunningham et al. 1995, Mdegela et al. 2009). It raises potential long term environmental and health concerns. Heavy metals are not biodegradable (Sobukola et al. 2010) and they accumulate in soil much longer than in other compartments of the biosphere (Lasat 2002), hence contamination is long term. Without remedial action, soil will never return to normal.
