변산반도 조간대 표층 퇴적물의 퇴적률 및 저서환경 변화

Abstract

To understand temporal variations in geochemical characteristics of intertidal surface sediments around Byeonsan Peninsula (in the middle of the western coast, Korea) after the construction of Saemanguem dyke, the sedimentation rate and various geochemical parameters, including mean grain size (Mz), water content (WC), ignition loss (IL), chemical oxygen demand (COD), and acid volatile sulfide (AVS), were measured along four transects (A.D lines) at monthly intervals from February 2008 to March 2009. The average monthly sedimentation rate ranged from -5.3 to 3.8 mm/month (mean <TEX>$-0.8{\pm}2.7\;mm$</TEX>/month), which showed an erosion-dominated environment in the lower part of the intertidal zone. In addition, surface sediments were eroded in summer and autumn, but were deposited in spring and winter. The Mz of surface sediments ranged from -0.8 to <TEX>$3.4{\varnothing}$</TEX> (mean <TEX>$2.8{\pm}0.5{\varnothing}$</TEX>), indicating that the surface sediments consist of coarser sediments (sand and slightly gravelly sand). The Mz of surface sediments did not show large monthly and/or seasonal variations, although the sedimentation rates of surface sediment showed large seasonal variation. This may be due to lateral shifting and effective dispersion of surface sediments by wind, tide, and longshore current. The concentrations of IL and COD in the surface sediments ranged from 0.2 to 2.9% (mean <TEX>$1.4{\pm}0.4%$</TEX>) and from 0.2 to <TEX>$18.5\;mgO_2$</TEX>/g-dry (mean <TEX>$3.9{\pm}3.4\;mgO_2$</TEX>/g-dry), respectively, which were slightly higher in spring than in the other seasons. This may be related to spring blooms of phytoplankton in seawater and/or benthic microalgae in surface sediments. On the other hand, no AVS concentrations were detected in surface sediments at any of the sampling stations during the study period.