The observations on the seasonal fluctuation and distributional characteristic of organic matters on surface sediments and its origin were carried out at the 25 stations in Keogeum-sudo, southern coast of Korean Peninsula from February to October in 1993. I made an analysis on the environmental factors for surface sediments such as temperature, ignition loss, chemical oxygen demand, pheopigment, total sulphide, water content, mud content in grain size, COD/IL ratio and COD/sulphide ratio. The results are as follows ; 1) The range of temperature on the surface sediments was between 6.2℃ and 24.6℃. The highest mean temperatuer of mud was 24.0℃ in summer, the lowest 6.6℃ in winter. 2) Ignition loss(IL) fluctuated between 1.2% in winter and 16.8% in spring, that is to say, the seasons of increasing in temperature were very high ignition loss. 3) Chemical oxygen demand(COD) showed the highest mean value of 20.52 ㎎/g dry in summer within the range of 15.46∼32.78 ㎎/g dry, while showed the lowest of 5.79 ㎎/g dry in winter within the range of 7.4∼17.39 ㎎/g dry. 4) Pheopigment concentrations showed the highest mean value of 4.85 ㎍/g dry in autumn within the range of 0.84∼9.21 ㎍/g dry, while it did the lowest mean value of 1.97 ㎍/g dry in summer within the range of 0.23∼4.83 ㎍/g dry. 5) Total sulphide (H2S) fluctuated between no detect(ND) in spring, and 2.43 ㎎/g dry in autumn. The highest mean value was 0.68 ㎎/g dry in autumn, the lowest was 0.16 ㎎/g dry in spring. 6) Water content(WC) and mud content in grain size showed the mean value of 43.2% within the range of 26.5∼59.7% and 91.0% within the range of 57.8∼99.2%, respectively. 7) By the analytical results on the source of organic matter, it had been dumped from the seaweed farms in Keogeum-sudo coastal waters.

To investigate size distribution and metallic elements of surface sediments in Hampyong Bay, the southwestern coast of Korea, sedimentological and geochemical studies on surface sediments are carried out. The surface sediments of Hampyong Bay are classified into gravel, muddy sandy gravel, gravelly muddy sand, gravelly sandy mud, mud facies in accordance with areal characteristics. The coarse sediments are distributed on the subtidal zone along the main tidal channel and southeast intertidal flat of Hampyong Bay. On the other hand, the fine sediments are dominated in northeast and west intertidal flat of Hampyong Bay. Most metallic elements except for Ba in the sediments are closely interrelated with fine sediments and mutually with each element. Ba is maybe related with sandy sediments and inversely related with carbonate contents. Normalized by Al content, the sediment do not show any remarkable metal enrichments influenced by resonable artificial or environmental factors.

In order to determine the changes of sediment facies and metal levels in surface sediments after the construction of Shiwha Lake, surface sediments were sampled at 8 sites located on the main channel monthly from June, 1995 to August, 1996 and analysed for 12 metals (Al, Fe, Mn, V, Cr, Co, Ni, Cu, Zn, Cd, As and Pb) by ICP/AES and ICP/MS. Two groups of sampling sites (the inner lake with 3 sites and the outer lake with 5 sites) are subdivided by the surface morphology; the inner lake is a shallow channel area with a gentle slope, while the outer lake is relatively deep and wide channel with a steep slope which has many small distributaries. After the construction of dam, fine terrestrial materials were deposited near the outer lake, which resulted in the change of major sediment facies from sandy silt to mud. With the deposition of fine sediments in the outer lake, anoxic water column induced the formation of sulfide compounds with Cu, Cd, Zn and part of Pb. Metal (Cr, Ni, Cu, Zn and Cd) contents in sediments increased up to twice within 2 years after the construction of dam. This is due to the direct input of industrial and municipal wastes into the lake and the accumulation of metals within the lake. In addition, frequent resuspension of contaminated sediments in a shallow part of the lake may make metal-enriched materials transport near the outer lake with fine terrestrial materials. As the enrichment of Cu, Zn, Cd and part of Pb in the Shiwha Lake may be related to the formation of unstable sulfide compounds by sulfate reduction in anoxic water or sediment column, the effect of mixing with open coastal seawater is discussed.