Species distribution of heavy metals in soil of Nansha economic zone of Guangzhou city

The HCl -HNO3-HF, HClO4 codigestion method and three-step BCR (Community Bureau of Reference) sequential extraction procedure method were used to analyse the contents and speciation of heavy metals (Zn, Pb, Cd, Ni, Cu and Cr) in Nansha economic zone of Guangzhou city. The results showed that the contents of Zn, Cd, Ni and Cu in soil exceeded the maximum permissible limits which setted by state environmental protection agency (SEPA) for soils in China, but the pollution was not obvious. Compared with the Guangdong soil background value, the contents of Zn, Pb, Cr, Ni, Cu, Cd in Nansha ecnomic zone had exceeded the background value, separately were 9.49, 4.9, 1.7, 4.29, 5.68, 11.06 times of the background value. In soil, Zn, Cu and Cr were dominantly released in the residual and oxides fractions, they accounted for 52.39%, 48.34%, 66.23% and 23.30%, 41.96%, 27.67% of their total contents,respectively; Pb was dominantly released in the oxidizable and residual fractions, they accounted for 46.88% and 31.48% of its total contents, respectively; Ni was dominantly released in the residual fractions, it accounted for 72.45% of its total contents; Cd wasdominantly released in the weak acid soluble and exchangeable ion fraction, they accounted for 41.81% and 27.55% of its total contents,respectively. The activity of Cd was obviously higher than the other heavy metal elements, and it will bring the highest risks to the environment pollution.