[Enrichment characteristics of heavy metals in heron eggs]

In this study, the eggs and tissues of black-crowned night heron, little egret, Chinese pond heron and cattle egret were sampled from the Dashu, Yuantong and Taizi mountains in Hefei areas of Anhui Province in April to June 2004, and the residual amounts of Cd, Pb and Cr in the samples were determined by atomic absorption spectrophotometry. The results showed that the test heavy metals could be detected at high levels in the eggshell, egg contents, and tissues of most samples. Eggshell and bone were the two main sites for heavy metals enrichment. Eggshell had significantly higher residues of the heavy metals than egg contents, implying that heavy metals could be excreted by eggshells. The residues of heavy metals in eggshell ranked as Cr > Pb > Cd, and had significant differences among species. Of the three heavy metals, Cr showed the most variation among species, being the highest in eggshell of Chinese pond heron and the lowest in that of cattle egret, but in egg contents, there was no significant difference among species. The variation of Cr residues among species was the second, being the highest in the egg contents of Chinese pond heron but not detected in that of cattle egret. The residues of Pb among species varied little. Since eggshell was easy to collect, it was practical to use it as the indicator to assess the pollution status of wetlands.