Characterization of the particle size fraction associated heavy metals in tropical arable soils from Hainan Island, China

Tropical arable soils were sampled from Hainan Island. The particle size fractions associated Cr, As, Cd and Pb were characterized and their leachability was analyzed as well. The pollution of heavy metals in the arable soils was not severe except Cr (204 mg kg(-1)) in Haikou. The distribution of heavy metals increased with decrease of particle size. Although the smallest fractions (< 53 mu m) occupied only 5.08-9.57%, they had the highest distribution factor (DF) of 3.50 for Cd, 2.11 for Pb, 1.73 for Cr and 1.09 for As, respectively. The contributions of micro-aggregates (< 250 mu m) to the total amount of heavy metals was 41.9% for Cr, 44.6% for As, 61.6% for Cd and 48.6% for Pb, respectively, and the second mass loading came from the particles of 250-1000 mu m. The residues of Cr, Cd and Pb were correlated positively with the contents of organic carbon as well as Fe in fractions, while a large variation distribution of As was found in particles, indicating its high activity in soil microenvironment. The lowest leachability was found in the easily migratory micro-aggregates, which should be taken into account in the future environmental risk assessment and soil remediation. (C) 2013 Elsevier B.V. All rights reserved.