Relationship and enrichment of heavy metals in soil of sewage irrigation area in Guangdong province, China

The research reveals the relationship and enrichment of heavy metals in soil of sewage irrigation area in Guangdong province, southern China. Samples were collected from topsoil (0-10cm) and subsoil (30-40cm), and the total concentrations of heavy metals were extracted by HNO3-HF-HClO4. It is concluded that Cu, Zn, Cd, and Pb may be homologous or combined pollution, and Mn and Cr may be also homologous in soil. According to the result of cluster analysis, it is shown that Se and As may have the similar environmental geochemical behavior in topsoil, because the existing forms of them in environment are mainly acid anions. We can conclude that a significant degree of metal pollution exists in soil of sewage irrigation area, particularly for Cd, Cu, Pb and Zn. The degrees of contamination of heavy metals in topsoil (CF of Cd 8.1, Cu 7.0, Zn 5.9, Pb 3.6, Ni 2.1, As 1.8, Cr 1.6, Se 1.5) were higher than that in subsoil (CF of Cd 6.0, Cu 3.4, Zn 3.7, Pb 2.7, Ni 2.0, As 1.6, Cr 1.5, Se 1.4). EF values show deficiency enrichment with Ni, Se, Cr and As, low enrichment with Cu, Zn and Pb, and moderate enrichment with Cd in topsoil in study area, while deficiency enrichment with Ni, Se, Cr, Pb and As, and low enrichment with Cu, Zn and Cd in subsoil in study area. It should be recognized that the hazards posed by food production in sewage irrigation areas may become a common hazard for human.