Sorption of mercury (II) in Amazon soils from column studies

The sorption of Hg (II) onto four different types of Amazon soils from the A-horizon was investigated by means of column experiments under saturation conditions and controlled metal load. Higher organic matter contents in the soil resulted in higher Hg (II) adsorptions, reaching values as high as 3.8 mg Hg g−1 soil. The amount of mercury adsorbed on a soil column (Q) shows a very poor correlation with soil clay content (r2 = 0.2527), indicating that Hg sorption in these topsoil samples is chiefly governed by the organic matter content. Desorption experiments using Negro River (Amazon) waters were conducted using soil saturated with Hg (II) in order to better understand the metal leaching mechanism. The amount of Hg (II) released from soils was around 30% of the total sorbed mercury upon saturation, suggesting that mercury sorption in the soils present in the catchment area of the Negro River basin is not a reversible process.