The utilization of biochar alone and in combination with compost for removal of potentially toxic metals accumulated in soils associated with land-use patterns

Abstract Potentially toxic metals in soils are a threat to food security and harmful to human because it enters the food chain through crop uptake. Hence, it is critical to know the levels of potentially toxic metals in soils due to agricultural land use patterns and how they can be removed from the soil. This review discussed the effect of different land-use patterns on heavy metal accumulation, their removal using biochar. A desktop review which employed PRISMA was used to put together information from peer-reviewed papers including journal articles, books, thesis and reports. It was shown that potentially toxic metals mainly found in the soil include; As, Cu, Cd, Zn, Cr, Co, Ni, Sb, Hg, Th, Pb, Si, and Se. The sources of these potentially toxic metals accumulation in soils were organic and inorganic fertilizer application, irrigation, pesticides and weedicides application and atmospheric deposition. However, different land-use patterns (greenhouse field, vegetable field soils, forest field, and maize field soil) had a significant accumulation of heavy metals (Cr, Ni, Cu, As, Cd, and Zn) due to increasing crop yield through the application of fertilizers and pesticides. Biochar was found to be effective in the removal of 18 to 40% of these potentially toxic metals from the soil. The mechanisms of removal were; precipitation, physical sorption, complexation, and ion exchange and electrostatic interaction. It can be concluded that biochar applied solely or in addition to compost has strong stability to remove heavy metals accumulated in soils due to land use patterns.