Use of sequential extraction to assess metal partitioning in soils

• Published in: Environmental pollution (1987) 2003-11, Vol.126 (2), p.225-233
• Main Authors: Kaasalainen, Marika, Yli-Halla, Markku
• Format: Article
• Language: English
• Subjects: Applied sciences; Biological and physicochemical properties of pollutants. Interaction in the soil; Cadmium - analysis; Copper - analysis; Earth sciences; Earth, ocean, space; Engineering and environment geology. Geothermics; Environmental Monitoring - methods; Exact sciences and technology; Finland; Geologic Sediments; Heavy metal pollution; Lead - analysis; Metallurgy; Metals, Heavy - analysis; Nickel - analysis; Pollution; Pollution, environment geology; Sequential extraction; Smelter; Soil and sediments pollution; Soil Pollutants - analysis; Soil profile; Soil texture; Zinc - analysis
• ISSN: 0269-7491; 1873-6424
• DOI: 10.1016/S0269-7491(03)00191-X

The state of heavy metal pollution and the mobility of Cd, Cu, Ni, Cr, Pb and Zn were studied in three texturally different agricultural soil profiles near a Cu–Ni smelter in Harjavalta, Finland. The pseudo-total concentrations were determined by an aqua regia procedure. Metals were also determined after division into four fractions by sequential extraction with (1) acetic acid (exchangeable and specifically adsorbed metals), (2) a reducing agent (bound to Fe/Mn hydroxides), (3) an oxidizing agent (bound to soil organic matter) and (4) aqua regia (bound to mineral structures). Fallout from the smelter has increased the concentrations of Cd, Cu and Ni in the topsoil, where 75–90% of Cd, 49–72% of Cu and 22–52% of Ni occurred in the first two fractions. Slight Pb and Zn pollution was evident as well. High proportions of mobile Cd, Cu and Ni also deeper in the sandy soil, closest to the smelter, indicated some downward movement of metals. The hydroxide-bound fraction of Pb dominated in almost all soils and horizons, while Ni, Cr and Zn mostly occurred in mineral structures. Aqua regia extraction is usefully supplemented with sequential extraction, particularly in less polluted soils and in soils that exhibit substantial textural differences within the profiles. Sequential extraction is most useful with soils with low metal pollutant levels.