In order to elucidate how the heavy metal content of short-neck clam varies with its growth, the contents of 11 kinds of metals, i.e., mercury, cadmium, lead, arsenic, zinc, copper, selenium, cobalt, manganese, nickel and chromium, in the edible portion were determined by atomic absorption spectrophotometry and colorimetric and fluorescence analysis.
Examination showed that there are three patterns, that is, increasing, constant and decreasing patterns.
The contents of mercury, cadmium, lead, and arsenic increased with the growth according to the following regression equations: y=10
6.3×10-3x-2.04, y=10
8.0×10-3x-1.11, y=10
4.3×10-3x-0.272 and y=10
1.2×10-2x-0.106 (y, mercury content; x, shell length). Four metals, zinc, copper, selenium, and cobalt, gave a constant pattern with a variation coefficient less than 7.7%. The last three metals, namely, manganese, nickel and chromium, fit a decreasing pattern with the regression equations: y=10
-1.4×10-2x+0.91, y=-5.4×10
-3x+0.50, and y=-2.1×10
-3x+0.20 respectively.
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