Abstract:

Heavy metals including Cd, Cu, Cr, Pb, As and Hg in oysters, razor clams and blood clams collected from
three breeding areas located, respectively, in Ninghai, Xiangshan and Zhoushan of Zhejiang province were investigated
by inductively coupled plasma mass spectrometry (ICP-MS) and atomic fluorescence spectrometry. Sequential extraction
procedure was introduced to determine metal speciation of Cd, Cu, Cr, Pb and organic and inorganic forms of arsenic and
mercury before and after boiling. The results showed that the contents of Cd, Cr, Cu, and Pb varied among three marine
shellfish, and significant correlations existed between Cu and Cd, and between Cr and Pb. Meanwhile, the percentage of
samples exceeding the standard limit of arsenic was 77.78% while Hg residues were lower than the standard limit. As
indicated by comparison of the contents of acid extractable, reducible, oxidizable and residual fractions of Cd, Cu, Cr, and
Pb before and after boiling, boiling had significant effect on speciations of Cd, Cu, Cr, and Pb, but had little effect on organic
and inorganic forms of arsenic and mercury. In conclusion, the content of heavy metal elements and the variation of metal
speciation before and after boiling can be used as indexes to evaluate the bioavailability of heavy metals in marine shellfish.

Key words: boiling, marine shellfish, heavy metals, speciation