| dc.description.abstract | The Feitsui reservoir supplies the water use for northern Taiwan. Hence, it water quality is closely linked to people’s well being. This study is concerned with the polycyclic aromatic hydrocarbons (PAHs) in the Feitsui reservoir. PAHs are an organic contaminants that have hydrophobic, toxic, carcinogenic, mutagenic and bioaccumulative. PAHs are generated from combustion or high temperature alteration of organic matters. PAHs is cycled through the environment until buried in sediments. The objective of this study is to investigate the composition and concentration of PAHs in settling particles and sediments, to assess the PAHs fluxes in settling particles, and to explore the compositional differebces of PAHs in settling particles and sediments. Finally, we hope to understand the sources of the PAHs.
The PAHs concentration in settling particles ranges from 1258 to 29112 ng/g. The PAHs concentration in sample from the 20m trap use higer than those in sample from the 70m trap. In general, the PAHs concentrations in settling particles are positively correlated with contents of organic carbon. When environmental PAHs concentration is too high, we cannot detect the correlation between PAHs concentration and organic carbon content. PAHs composition in settling particles were special in March, April, August and September, 2005. In frist two months, the PAHs compostion was dominated by pyrene In the other two months, it was dominated by dimethylnaphthalene.
The range of PAHs concentrations in sediments were between 330～804ng/g, and showed low correlation with organic carbon contents. The PAHs concentrations in sediments collected from cross-section No.15 had the highest values, the maximum occurred at 6 cm below surface. The principle compound was perylene.
In gernal, the PAHs flux of settling particles was between 4 and 465 mg/m2/day with a trend similar to that of the mass flux of settling particles flux. It was enhanceced by the turbid flow. The PAHs flux in March and September showed pattern different from the mass flux, because the PAHs concentration in settling particles in March and September were especially high.
Based on principle component analysis (PCA), the PAHs composition of settling particles and sediments can be divided into four fypes: the PAHs composition of surface sediments and suspended particles, which represents the background condition in the Feitsui reservoir; Second, the PAHs composition in settling particles in March and April, which was dominated by pyrene and might come directly from atomospheric deposition; Third, the PAHs composition in settling particles in August and September, which might come from the surface soils brought into the reservoir by strong typhoon precipitation; Fourth, the PAHs composition in sediments from cross-section No.15, which very high concentrations of perylene. The last type may have been contributed from a nearly tributary. The PAHs compositions of sediments and settling particles were significant different. The PAHs concentration in sediments were considerably lower than those in settling particles. The difference was attributed to degradation of PAHs in sediments and mineral dilution.
Finally, we used isomer ratio to identify the PAHs sources, we found that the PAHs in sediments may have originated mainly from combustion of organic matters; whereas the PAHs in settling particles may have originated from mainly petroleum. | en_US |