시화호 및 인근 연안해양 퇴적물의 지화학 성분과 유기물 분해 특성

Abstract

본 연구에서는 조력발전 가동에 따른 시화호 및 인근 연안해양 퇴적물 내 지화학적 분포 특성과 유기물 분해율의 조절 요인 파악과 함께 퇴적물로부터 용출된 영양염류가 수중 생태계에 미치는 영향에 대해 조사하였다. 조력발전 가동 중인 2014년에 시화호 내 상류 정점 L1과 시화호 외측 수문 부근 정점 E5에서 공극수 내 용존 무기탄소, 암모니아 및 인산염은 조력발전 가동 전보다 현저하게 감소하였다. 2015년 7월에 조사한 시화호 인근 연안 해양 퇴적물 공극수 내 암모니아. 인산염, 철의 농도는 육지와 인접해있는 정점(E0. E1 및 E3)에서 외측 정점(E5와 E7)보다 상대적으로 높게 나타났다. 퇴적물 내 입자성 유기탄소와 공극수 내 용존 유기탄소는 소래포구 인근 정점(E0)에서 가장 높게 나타났으며, 수문 부근으로 갈수록 점차 낮아지는 경향을 보였다. 이와 유사하게 퇴적물 내 산소소모율, 혐기성 유기물 분해율 및 황산염 환원율은 정점 E0에서 가장 높게 나타났으며, 수문 부근 정점(E5)으로 갈수록 점차 낮아지는 경향으로 나타났다. 이러한 유기물 분해율은 퇴적물 내 입자성 유기탄소와 밀접한 상관관계로 나타났으며, 특히, 공극수 내 용존 유기탄소와 더욱 밀접한 상관관계로 나타났다. 저층 영양염 용출률은 육지와 인접해 있는 정점(E0, E1 및 E3)에서 일차생산자가 필요로 하는 용존 무기질소와 무기인의 121-509%, 26-178%에 해당되는 양을 공급하고 있었다. 이러한 결과들은 (1) 조력발전을 통한 해수 유통량의 대폭적인 확대로 해수의 물리적 혼합을 증가 시켰고, 퇴적물 내 공극수 교환(tidal flushing)으로 인해 유기물 분해산물의 재산화 및 수층으로 용출을 야기 시킨 것으로 판단되며, (2) 시화호 인근 연안 해양 퇴적물 내 산소 소모율, 혐기성 유기물 분해율 및 황산염 환원율은 인근 하천을 통해 유입된 유기물 유입량에 의해 조절되며 특히, 공극수 내 용존 유기탄소와 밀접한 상관관계로 나타났고, (3) 육지와 인접해있는 시화호 인근 연안 해역은 퇴적물로부터 매우 극단적인 영양염류의 용출률을 보이고 있었으며, 이는 수층의 저산소(hypoxia) 형성과 부영양화를 야기하여 식물플랑크톤 및 유해조류의 대증식을 야기 시킬 수 있다.|I investigated (1) geochemical properties in the sediment to understand the impact of tidal power plant operation at the Lake Sihwa (L1, L2, L3, L4, and L5) and the neighboring coastal waters (E2, E4, E5, E6, and E7), and (2) sediment oxygen demand (SOD), anaerobic carbon oxidation and sulfate reduction rates to explain the pathway of organic carbon oxidation and (3) benthic nutrient flux (BNF) to evaluate the relative contribution of BNF to the nutrient requirements of pelagic primary producer growth in the sediments of the coastal areas nearby the Lake Sihwa (E0, E1, E3, E5, and E7). The concentrations of dissolved inorganic carbon (DIC), ammonium, and phosphate in pore-water decreased in 2014 (after operation of the tidal power plants) than in 2006 (before operation of the tidal power plants). In July 2015, concentration of nutrients in pore-water, such as DIC, NH4+, and PO43- were higher at adjacent to land sites (E0, E1, and E3) than those at outside sites (E5 and E7). Particulate organic carbon (POC) in the sediments and dissolved organic carbon (DOC) in pore-water appeared the highest concentrations at the site E0 located at Sorae-port, and these organic carbon concentrations gradually decreased toward to the floodgate. Correspondingly, SOD and rates of anaerobic carbon oxidation and sulfate reduction were the highest value at the site E0, and then they gradually decreased toward to the sites E5 located floodgate. These carbon oxidation rates have a positive correlation with the concentrations of organic carbon content in the sediment. Especially, the concentration of DOC in pore-water more closely related to the organic carbon oxidation rates than the concentration of POC. The BNF at sites E0, E1 and E3 supplied 121-509% of the N demand and 26-178% of the P requirement for primary production during the sampling period. Overall results indicate that (1) massive expansion of seawater circulation through tidal power plants increased physical mixing, and tidal flushing caused reoxidation and fluxes of organic matter mineralization products into overlying water; (2) total aerobic respiration rate calculated from SOD, anaerobic carbon oxidation rate, and sulfate reduction rate in coastal sediments around the Lake Sihwa are regulated by either amount of organic carbon introduced from land or existence form of organic carbon in the sediment and (3) benthic organic mineralization and nutrients fluxes are stimulated by the enrichment of organic carbon driven from land, and benthic-pelagic coupling appear to be tightly, which may act as potential risks in bring the eutrophication and hypoxia in the coastal waters.; I investigated (1) geochemical properties in the sediment to understand the impact of tidal power plant operation at the Lake Sihwa (L1, L2, L3, L4, and L5) and the neighboring coastal waters (E2, E4, E5, E6, and E7), and (2) sediment oxygen demand (SOD), anaerobic carbon oxidation and sulfate reduction rates to explain the pathway of organic carbon oxidation and (3) benthic nutrient flux (BNF) to evaluate the relative contribution of BNF to the nutrient requirements of pelagic primary producer growth in the sediments of the coastal areas nearby the Lake Sihwa (E0, E1, E3, E5, and E7). The concentrations of dissolved inorganic carbon (DIC), ammonium, and phosphate in pore-water decreased in 2014 (after operation of the tidal power plants) than in 2006 (before operation of the tidal power plants). In July 2015, concentration of nutrients in pore-water, such as DIC, NH4+, and PO43- were higher at adjacent to land sites (E0, E1, and E3) than those at outside sites (E5 and E7). Particulate organic carbon (POC) in the sediments and dissolved organic carbon (DOC) in pore-water appeared the highest concentrations at the site E0 located at Sorae-port, and these organic carbon concentrations gradually decreased toward to the floodgate. Correspondingly, SOD and rates of anaerobic carbon oxidation and sulfate reduction were the highest value at the site E0, and then they gradually decreased toward to the sites E5 located floodgate. These carbon oxidation rates have a positive correlation with the concentrations of organic carbon content in the sediment. Especially, the concentration of DOC in pore-water more closely related to the organic carbon oxidation rates than the concentration of POC. The BNF at sites E0, E1 and E3 supplied 121-509% of the N demand and 26-178% of the P requirement for primary production during the sampling period. Overall results indicate that (1) massive expansion of seawater circulation through tidal power plants increased physical mixing, and tidal flushing caused reoxidation and fluxes of organic matter mineralization products into overlying water