Uptake and depuration of water-soluble fractions (WSF) of crude oil by the bivalve Corbicula fluminea (Müller) from Shatt Al-Arab river

This study includes laboratory uptake and depuration experiments. The bivalve C. fluminea is exposed to 5ml of WSF of Nahran–Umar crude oil for each liter of river water for 48 hours in the static toxicity test system. The exposure water and animals are periodically taken for analysis of total hydrocarbons concentrations by spectroflurometer. After the exposure period is over, the bivalve transferred to clean river water for depuration period of 48 hours. The experiments show that there are no mortalities due to WSF of Nahran–Umar crude oil. The bivalve is usually active during the 12–16 hours of the experiments. Hydrocarbons concentrations in the exposure water decreased are slowly in a linear fashion so that no measurable concentrations remained after 32 hours. Hydrocarbons accumulated by the bivalve are slowly during the first few hours of exposure. After 2 hours of exposure, the concentration of hydrocarbons is approximately 0.38 ppm in water, while in tissues it is 4.8 ppm. After 20 hours, hydrocarbons are present in water at a concentration of 0.09ppm, while the bivalve tissues contained 17.7 ppm hydrocarbons. After 25 hours of exposure, the hydrocarbons concentration decreased in the bivalve tissues. At the end of the exposure period, the bivalve contains approximately 7.4 ppm. After 48 hours in clean river water, tissues burden decreased to 0.22 ppm of hydrocarbons. The bivalve remained contaminated with small concentrations of hydrocarbons for 20 days. The complete depuration occurred at 26 days.