The Mean Particle Size, Organic Carbon, and Salinity Distribution of the Surface Sediments in the Hwangdo Tidal Flat, Taean, Western Korea

Abstract

The Hwangdo tidal flat is located in Cheonsu Bay in Taean-gun, Chungcheongnam, on the west coast of Korea. Cheonsu Bay is a semi-closed bay characterized by various environments, such as channels, sand bars, small islands, and tidal flats. This study assessed the field measurement of ellipsoid height using a real-time kinematics global positioning system (m) and used laboratory analyses to obtain geological data on sediment type in a pilot study area. In October 2022 (n = 107), the mean particle size (phi), total organic carbon (TOC) (%), total nitrogen (TN) (%), total carbon (TC) (%), salinity (psu) in porewater, specific dry bulk density, porosity (%), and water content (%) of surface sediments were analyzed. The sedimentary facies ranged from coarse sand to fine silt, including sandy Silt (sZ) > muddy sand (mS) > slightly gravelly sandy mud ((g)sM) and etc. The sedimentary phases were classified following Folk and Ward (1957). Organic matter was characterized based on particle size analysis, with verification of each experimental result. The C/N (TOC/TN) ratio had values of 10 or less, suggestive of influences by organisms of marine origin rather than land origin. The salinity distribution was correlated with the sedimentary phase, organic matter content, tidal flat elevation (location), and exposure time after low ebb tide. The salinity was higher in highland tidal flats where the sedimentary facies was fine, the organic matter concentration was high, and the exposure time was long. This result suggested that energy was relatively low in the tidal flat near Hwangdo channel. These data will be useful for understanding the changes in the sedimentary environment of the Hwangdo tidal flat and establishing conservation management plans for this area. In the future, the geological environment characteristics dataset will be used as basic data to assess changes in the tidal flat topography and sedimentation environment.