Environmental Impact of Potentially Toxic Elements on Tropical Soils Used for Large-Scale Crop Commodities in the Eastern Amazon, Brazil

The Amazon soils demand high rates of fertilizer application to express high agricultural potential, making it necessary to carry out frequent monitoring of ecological functions and biogeochemical processes in this important biome. The concentrations of As, Ba, Cd, Co, Cr, Cu, Hg, Ni, Pb and Zn and contamination indexes were studied in Oxisol and Ultisols cultivated with citrus (Citrus sinensis (L.) Osbeck), oil palm (Elaeis guineensis Jacq.) and black pepper (Piper nigrum L.), at 26, 10 and 5 years of implantation, respectively. The potential risk of contamination was estimated by the enrichment (EF) and bioaccumulation (BAF) factors. Moderate enrichment of Ba, Pb and Zn (2 < EF < 5) and significant enrichment of As and Cu (5 < EF < 20) were observed. In addition, the following orders of bioaccumulation were found: oil palm-Cu > Zn > Hg > Ni > Ba > Co > As > Cr > Cd approximate to Pb; black pepper-Zn > Hg > Cu > Ba > Ni > Co > Pb >> As > Cr > Cd; and citrus-Hg > Ni > Ba > Zn > Co > Cu > As > Pb >> Cr > Cd. However, all elements are in concentrations below the prevention and investigation values established by Brazilian legislation, that is, the management practices in the crops studied are not contributing with damage to soil and human health risks.