Chromium Displacement in Subtropical Soils Fertilized with Hydrolysed Leather: A Laboratory Study

Prolonged use of biosolids with high metal content may result in diffuse pollution across large regions, especially if such ions can move freely through the soil profile and reach underground water sources. The objective of this study was to verify whether Cr added to the soil surface in the form of hydrolysed leather or a soluble salt would migrate over significant distances in four subtropical soils differing in physical, chemical and mineralogical properties. Horizontal and vertical mobility were assessed in Petri dishes and small pots, respectively, using low (12 mg kg^-1 soil) and high Cr levels (150 mg kg^-1 soil) added to the soil surface. Irrespective of concentration, soluble Cr salts were found to move more easily in soils with low organic matter and clay content. Contrarily, Cr added as hydrolysed leather exhibited negligible mobility and tended to accumulate in the vicinity of application.