Presence and origin of polycyclic aromatic hydrocarbon in sediments of nine coastal lagoons in central Vietnam

摘要

Several natural and anthropogenic processes can lead to the formation of polycyclic aromatic hydrocarbons (PAHs), a well known class of compounds, many of which with mutagenic and carcinogenic properties (Nielsen et al., 1995), that are regarded as priority pollutants by the US Environmental Protection Agency (US EPA, 1993). Anthropogenic sources include combustion of fossil fuels, coal gasification and liquifkation processes, petroleum cracking, waste incineration and production of: coke, carbon black, coal tar pitch and asphalt, (McCready et al., 2000). Another common anthropogenic source of PAHs is spillage of fossil fuels, both unrefined and refined products. PAHs also stem from natural combustion sources such as forest fires, and certain compounds (perylene and retene) are thought to be diagenetically produced (Wakeham et al., 1980). Because of their hydrophobic nature, PAHs in the aquatic environment are easily adsorbed onto settling particles and finally accumulate in sediments. This adsorption-settling process is continuous over time, therefore sediments can act as recorders of con- taminant inputs as well as of general environmental change over time (Kannan et al., 2005). It follows that the study of sediment records can provide information on levels, history and trends of pollutants in aquatic environments. Moreover, under particular erosive and resuspending conditions, sediments can represent a source for toxic substances in aquatic environments and may affect wildlife and humans via the food chain.