The Microbioremediation Of Polycyclic Aromatic Hydrocarbons (PAHs) Pollution In Marine Environment

The investigation of the pollution level of polycyclic aromatic hydrocarbons (PAHs) and the distribution characteristics of PAHs-degrading bacteria in surface water and sediments has been conducted at six locations in Xiamen harbor (24?9' N, 118?4' E) on spring, summer and autumn cruises in 2001. The enrichment culture method was used to isolate the high molecular weight PAHs-degrading bacteria from samples contaminated with PAHs (pyrene, phenanthrene and fluoranthene) in order to have a better understanding of biodegradation mechanism of PAHs in marine environment.In this study, the level of sixteen individual polycyclic aromatic hydrocarbon compounds has been identified as priority pollutants in different seasons in Xiamen harbor. The results showed that the concentration and composition of PAHs in the surface water were unstable. The pollution level of PAHs in April and October were higher than that in July. PAHs in the surface water were mainly dominated by naphthalene (2 rings) in April, acenaphthene (3 rings) in July and chrysene (4 rings) in the October. The concentration of anthracene and benzo(a)pyrene in surface water was higher than the toxicity guidelines. The origin of PAH pollution in surface water of Xiamen harbor was mostly petrogenic.PAHs in sediments were mainly dominated by high molecular weight PAH components (4-6 rings). Fluoranthene and pyrene were the most dominant at different seasons and stations. The change of total PAHs concentration was insignificant in different seasons, but the level of high molecular weight PAH compounds showed an increasing tendency. Comparing with the results obtained from Xiamen harbor in 1993, the pollution level of PAH in sediments has decreased and the origin of PAH was the same as that found for the surface water.The distribution characteristics of PAH-degrading bacteria were realized for the first time in Xiamen harbor during the two cruises in surface water and sediments of Xiamen Western harbor. For this purpose, the spray-plate technique with modification was used to numerate PAH-degrading bacteria. The results showed that, PAH-degrading bacteria were abundant in both of surface water and sediments of Xiamen Western harbor. The numbers of PAH-degrading bacteria were more than 103CFU/mL in surface water and 104 CFU/g in sediments during summer season. However, during the autumnthe numbers of PAH-degrading bacteria were more than 102CFU/mL in surface water and 103 CFU/g in sediments.In the surface water, the concentration of high molecular weight PAH compounds fluoranthene and pyrene was very low during the two cruises. No correlation was found between the concentrations of high molecular weight PAH compounds and their degrading bacteria numbers. The positive correlation was found between the concentrations of low molecular weight PAH compounds (fluorene andphenanthrene) and their degrading bacteria numbers. This may imply that the inducement of high molecular weight PAH compounds to bacterium was limited by their low concentration in the surface water, high chemical stability and hydrophobicity and short exposure time. Consequently, the numbers of high molecular weight PAH compounds degrading bacteria might not indicate the extent of PAHs contamination in the surface water.In the sediments, positive correlation was significantly found between PAH-degrading bacteria numbers and PAHs concentration, expect the station 6. Those suggest that the relationship between the concentrations of high molecular weight PAH compounds and their degrading bacteria numbers is only significant for highly contaminated sites and long-term exposure. The PAHs-degrading bacteria number may indicate the PAHs pollution at some extent in the relative stable sediment environment, but it would not be omitted to well consider other influential factors.The enrichment of three pure cultures (PYSP1, PYSP6 and PYSP22) has been done successfully by using a spray plate method with pyrene as the sole carbon source. Other three pure cultures (FLSP2, FLSP6 and FLSP8) were is...