The understanding of the contamination of persistent organic compounds (POPs) and toxic chemicals in the riverine and estuarine environments is of great concern because of the detection of the residues in various environmental media. Since these compounds have highly affinities for particulate matters, one of their major sinks is thought to be the river and marine sediments. Therefore, the investigation of the distribution of POPs and heavy metals in sediments can provide a valuable record of contamination in the aquatic environments. The purpose of this project is to understand the composition and distribution of POP residues and heavy metals in surface sediments from the riverine and estuarine environments of the Erh-jen and Lan-yang Rivers. Also, the spatial and temporal changes and the environmental fate of toxic chemicals were discussed. Moreover, principal component analysis (PCA) and chemical potential were applied to the data in order to provide a characteristic fingerprint of the sources and to identify the distribution of pollutants in Taiwan. The distribution of heavy metals in Erh-jen River can be classified into three groups. The first group is Co, As and Hg which there is no obvious pollution source. The contamination of Zn, Cu, Ni, and Cr is mainly attributed to the discharge from San-yeh-kung River, a highly polluted tribute of Erh-jen River. Moreover, the contamination of As and Pb existed another pollution source, which is probably from the vicinity of Wan-Li pumping station. Several organochlorine pesticide (OCP) residues were also detected in sediments of Erh-jen River. However, the concentrations of metabolites were higher than those of parent compounds, showing that the contamination of OCP is mainly from the aged and weathered agricultural soils and transported by surface runoff to the river sediment.Lan-yang River is one of the representative non-polluted river in Taiwan. The concentration of heavy metals were, in general, lower th

sediment,persistent organic pollutants,sediment quality guideline