Iron, Aluminium and Titanium in Shells of Short-necked Clams

Abstract

Iron, aluminium and titanium in the shells of Ruditapes philippinarum (Adams and Reeve), collected at 7 different points of seashores in Nagasaki Prefecture (136 samples), were determined by photometric analysis in order to study the regional difference of the trace element contents. The mutual relations of the amounts of elements in shells and the concentration factor of each element from the sea water were also discussed.
The contents of the elements were found as follows: iron; 17-230ppm, aluminium; 20-230ppm, and titanium; 2.0-12ppm (calcium; 36.5-38.5%). The variation of the value of contents among the shells sampled in different localities was not larger than that of the shell taken at a same location (Table 3). Thus there was no marked regional difference. The dependence of the trace element contents on the size of a shell was hardly observed. The contents of iron, aluminium and titanium in the shells collected at 2 points around Omura Bay were generaly lower than those sampled at 2 points around Ariake Sea. Plots of the content of aluminium or titanium against that of iron gave a semi-linear relation (Figs. 4-6). This finding suggests that these elements show similar behavior in the process of shell formation. The concentration factors of calcium, iron, aluminium and titanium from sea water were 940, 7700, 8600 and 5900, respectively. The results show that the trace elements are more concentrated from sea water than calcium, the main element.