Study On Bioavailability Of Bullacta Exarata To Polycyclic Aromatic Hydrocarbon

As one of typical persistent pollutants in Tianjin's coastal zone, PAHs have the properties of persistence, bio-refractory and high toxicity, which has caused serious harm to environment, organism and human health. Now people gradually are realizing the necessity and urgency of taking effective measures to restore damaged ecological environment. Therefore, quantitatively analyzing the concentrations and distribution of PAHs in surface sediments and dominant species Bullacta exarata sampled from the typical intertidal zone, studying on the bioavailability of PAHs to Bullacta exarata and desorption behaviors of PAHs in sediment have great significance for ecological risk assessment, selecting reasonable remediation technologies and making feasible reparation strategy.Concentrations and distribution of 10 PAHs in surface sediments and Bullacta exarata sampled from the typical damaged intertidal zone were quantitatively analyzed by GC/MS, the main polluted sources in this area were discussed. The results showed that the concentrations of 2,3 ringed PAHs compounds in all detected PAHs were the most dominant both in sediments and organisms. The main source of PAHs in the studying area might be petroleum-derived contamination mixing incomplete combustion of the fossil fuel. According to sediment quality criterion, the concentration of naphthalene, fluorene, phenanthrene and anthracene exceed the risk low (ERL) values, which might be a certain potential toxic effect to the ecosystem of intertidal zone.The acute toxicity and bioaccumulation of Phe selected as a representative PAHs to Bullacta exarata was studied by simulation experiments in lab. The testing result showed that the theoretical median lethal concentration (LC50) value of Phe to Bullacta exarata was 73.6 mg/kg and the LC50 value was decreased with the increase of exposure time. At different contamination levels of Phe, the BSAF values were various for Bullacta exarata. With Phe concentration increasing in sediments, the accumulation of Phe in Bullacta exarata was increases significantly. Phe fresh spiked in sediments was biological utilized easily correspondingly with BSAF>1, when Phe in sediemnt was aged for 100d, Phe would be sequestrated by organic matters, which slowed down the releasing rate and reduced the bioavailability, so BSAF was less than 1.The sorption/desorption behavior of Phe in sediments from ecological demonstration area were studied using multiple cycles of sorption/desorption experiments and the desorption data were predicted using a new desorption model 'Dual-Equilibrium Desorption (DED) model'. The result showed that the sorption of both naphthalene and Phe agree well with the conventional linear sorption isotherm. While the desorption curve which showed an irreversible phenomenon was deviation from sorption isotherm but it could be predicted well with the DED model. In summary, this paper had a preliminary study on the bioavailability of PAHs contaminants to Bullacta exarata, which provided scientific basis for the environmental monitoring, ecological risk assessment and bioremediation of estuary and intertidal zone.