Sequential Extraction of Some Heavy Metals in Southwest Giza Soil, Egypt

Abstract

The pollution of agriculture soil in southwest Giza, Egypt with As, Cd, Pb and Cr were assessed by the application of Index of Geoaccumulation (Igeo) and five steps sequential extractions technique. The results indicated that the soils are muddy sand, alkaline (pH ≈ 8.3), calcareous (CaCO3>5%) and have low organic matter (3.1%). Soil contains about 142.8, 1.7, 123.5 and 209.1 ppm of As, Cd, Pb and Cr, respectively. The Igeo indicated that the soils of the study area ranged from uncontaminated-moderately to extremely contaminated. The sequential extraction explained the incorporation of Pb and Cr in the residual fraction and the incorporation of As and Cd in the carbonate fraction. The exchangeable fraction contains 9, 7.9, 5.1 and 2.6% of As, Cd, Pb and Cr extracts, respectively. The environmental risk in the study area comes from the presence of 10.4 ppm As in the exchangeable fraction. The risk assessment code illustrated that Pb ranged from low to medium risk, Cr medium to high risk, As high to very high risk and Cd shows very high risk. These results reflect the mixed sources (geogenic and anthropogenic) of metals in the soil of the study area.