낙동강 하구 갯벌 퇴적물에서 강을 통한 질산염 유입에 따른 질소순환의 계절 변화

Abstract

We investigated seasonal variation of sediment-water oxygen and inorganic nitrogen fluxes, and denitrification at tidal flat sediments located in the Nakdong River Estuary from July 2005 to September 2006. Net oxygen fluxes, measured with sediment incubations at in situ temperature, varied from -37.0 to . Oxygen fluxes into the sediments from the overlying increased due to the increased temperature. Denitrification rate () in this study was higher compared to the other Korean coast measured with the same method. Denitrification showed the same seasonal variation as oxygen fluxes. Denitrification rate based on -nitrate showed a strong correlation with nitrate flux into the sediments from the overlying water. Denitrification via water column supplied nitrate (), calculated from Isotope pairing technique, also correlated well with nitrate flux into the sediments. Nitrate from column seems to account for seasonal variation of denitrification in Nakdong River Estuary. To understand general patterns and trends of biogeochemical processes of sediments in the Nakdong River Estuary, we categorized biogeochemical fluxes measured in this study according to direction and sizes of fluxes. Type 1(high oxygen and inorganic nitrogen fluxes into the sediments and high denitrification) occurred in summer, whereas Type 2(low oxygen and inorganic nitrogen fluxes into the sediments and low denitrification) occurred in rest of the season. Intertidal flat sediments seem to react sensitively to influence of freshwater from the Nakdong River.