ABSTRACT
Copper (Cu) and zinc (Zn) are microelements essential to plants, and therefore plants may be affected by deciencies when Cu and Zn concentrations are low in the soil solution. However, both elements may cause phytotoxicity when their concentrations increase. Cu and Zn concentrations in soil are generally dependent on parent material, showing higher levels in basic rocks and lower levels in granite and limestone (Alloway 1990). In addition to being natural constituents, Cu and Zn enter soil via benecial agricultural additives such as lime, fertilizers, manure, herbicides, fungicides, sewage sludge, and compost. Other sources, such as mine wastes, y ash, and atmospheric deposits, may increase the heavy metal concentration in soils (Arias et al. 2001; Kabata-Pendias and Pendias 2001) and may cause damage to plants, diminish agricultural yields, and decrease the quality of natural waters in the environment. Cu and Zn can cause toxicity to a broad range of organisms and may accumulate in the food chain, causing deleterious effects in terrestrial and aquatic ecosystems. Cu toxicity affects annelids, algae, and fungi in a very relevant manner, while Zn toxicity is generally low (unless that affecting to annelids) as compared to that of other heavy metals and metalloids (Ross and Kaye 1994).
