Accumulation of petroleum hydrocarbons and heavy metals in clams （Ruditapes philippinarum） in Jiaozhou Bay, China

Accumulation and distributions of aliphatic and polyaromatic hydrocarbons (PAHs) and heavy metals were measured in tissues of the clam Ruditapes philippinarum collected from 5 sites in Jiaozhou Bay,Qingdao,China.The concentrations of total aliphatic hydrocarbon and PAHs ranged from 570 to 2 574 ng/gdw (gram dry weight) and from 276 to 939 ng/gdw,in the most and least polluted sites,respectively.The bio-accumulation of hydrocarbons and PAHs in the clams appeared to be selective.Aliphatic hydrocarbons were predominantly represented by short chain (<nC23) n-alkanes,suggesting that petroleum hydrocarbons were likely the major contamination source.The selective uptake of 3 and 4 ring PAHs,such as naphthalene,fluorene,phenanthrene,fluoranthene and pyrene,by the clams was probably related to the physiological and bio-kinetic processes that were energetically favorable for uptake of compounds with fewer rings.Accumulation of the metals Cd,Cu,Zn,Pb,Cr,Hg,and As in the clam tissues also showed high variability,ranging from 0.043 to 87 μg/gdw.Among the 7 detected metals,Zn,Cd,Cu,and As had a particularly high potential of accumulation in R.philippinarum.In general,a positive correlation was found between the tissue concentrations and sediment concentrations of hydrocarbons and of some metals.Our study suggests that moderate contamination with polyaromatic hydrocarbons,and low to moderate contamination with metals,currently exists for clam R.philippinarum in Jiaozhou Bay,in comparison with other regional studies.A long-term monitoring program is certainly needed for assessment of the potential ecological influence and toxicity of these contaminants of R.philippinarum in Jiaozhou Bay.