Accumulation of some potentially toxic metals and polycyclic aromatic hydrocarbons (PAHs) in marine clam Liochoncha ornata collected from the Omani Sea

Clam samples of Liochoncha ornata were collected for a period of one year from July 2009 to June 2010 at monthly interval. The soft tissue of clams was analyzed to detect some potentially toxic metals and polycyclic aromatic hydrocarbons (PAHs). Accumulation of Hg, Cd and Pb in the clam tissues showed variability with a mean concentration of 0.011±0.009, 1.769±0.942 and 0.015±0.039 µg/g wet weight for Hg, Cd and Pb, respectively. Cadmium had recorded a particularly high potential of accumulation in L. ornata.  The bioaccumulation of PAHs in the clams appeared to be selective and ranged from 4.80 to 12.0 ng/g; wet weight. The most carcinogenic PAHs, such as benzo (a) pyrene and dibenz (a,h) anthracene, were in all cases below the limits of detection. No distinctive relationship was found between different size class and contaminant uptake by the clam. The concentrations of both of Pb and Hg  in L. ornata, were found to be below the safe limits suggested by various authorities and thus gave no indication of pollution by such elements. However, continuous monitoring of these and other pollutants in the coastal marine ecosystem is advised.   Key words: Clam, Mercury, Cadmium, Pb, polycyclic aromatic hydrocarbons (PAHs), Oman.