하구및 연안생태Coastal management 2015 년 가을학기

Estuarine chemistry Sun energy  energy rich OM: photosynthesis or chemosynthesis  fuel biotic activity  dissipated into heat Biotic chemical compounds are conserved “one organisms waste become another’s nutrients”

Estuarine chemistry 1. Chemical composition of fresh and salt water Chemical processes in an estuary depends on the quantity and kind of materials transported by the fresh and salt water sources ” Chemical reactions that occur in fresh and salt water The resident time of river water in the estuary 1. Chemical composition of fresh and salt water 2. major oxidation-reduction reactions 3. metabolic gases 4. Cycling of biologically important nutrients

Estuarine chemistry Metals : from river; particulate forms; Fe, Mn River water: variable composition Salts from rock weathering precipitation (seawater spray, wind eroded dust) Sea water: uniform ; major minor component Biologically important compounds from river Silicon, iron, N, P Chemically important compounds from ocean; Sulfate, bicarbonate Metals : from river; particulate forms; Fe, Mn Dissolved particulate conversion Adsorption or desorption Coagulation, flocculation, precipitation Biotic assimilation, excretion

Behavior of dissolved ions Adsorption into silts: highly charged ions:PO43- 80~90% of is trapped Flocculation: coalescing of colloidal particles; depending on salinity: mostly occurs at 0~5 ppt Clay tend to have (- charges) ; Repulsion in fresh water; stable suspensions Attractive in salty water; agglomerates into flocs - charged  neutral ; van der Waals force dominates This trapping + estuarine circulation = mechanism for trapping chemicals into sediment

Behavior of dissolved ions Reactant approach Observe dissolved material with salinity; see if it is conservative Effective when sea and freshwater concentration is very different Mixing diagram; NO3, Sio2 sink in summer; conservative in winter NH4 source in summer Mn; complex Basic assumptions Riverine end member is constant over the mixing time No tributaries Provide no insights into the removal mechnism Product approach Measure flocculent material Fe, Mn,Al, P is removed by flocculation between 0-18 ppt Only explains one mechanism Only good for some dissolved materials

Redox reactions POM eventually comes to rest on sediments Energy source ; electron donor Respiration: oxidation-reduction (redox) reactions; transfer of electron from one material to another Energy flow in estuary is regulated by electron acceptor !!!: 고등 생물에게는 익숙치 않은 개념 ; 먹이?와 공기? Electron acceptors O2 ; exhausted in sediment SO42- ; dominant; sulfate reduction produce hydrogen sulfide

Aerobic respiration C6H12O6 + 6O2 6CO2 + 6H2O E

Quantifications oxidation of glucose (C6H12O6) C6H12O6 + 6O2 ---> 6CO2 +6H2O 276 g 192g 264g 108g 1g 0.69g 0.96g 0.39g

C6H12O6 + 6O2 ---> 6CO2 +6H2O 276 g 192g 264g 108g 발열량: (565+327)-217=675 kcal 1g 0.69g 0.96g 0.39g 발열량: 675/276 = 2.44 kcal=2440 cal 1g C의 에너지 2440 x 276/72=9.353kcal

The Electron tower CO2/glocose 2H+/H2 CO2/methanol CO2/Acetate Eh0 (volts) DG0 per 2 electrons 10 Kcal steps CO2/glocose -0.50 -0.40 -0.30 -0.20 -0.10 0.0 +0.10 +0.20 +0.30 +0.40 +0.50 +0.60 +0.70 +0.80 +0.90 2H+/H2 CO2/methanol CO2/Acetate SO42-/H2S Fumarate/succinate NO3- /NO2- NO3- /N2 Fe3+/Fe2+ O2/H2O

Heterotrophy (mainly in lake) Aerobic respiration give the highest growth yield for the bacteria. O2 is very poor, only upper mm (millimeter) of sediment have. So the lower heterotrophic activity ( reaction) needn’t O2 become important, degrade these organic material to inorganic material.. Vertical position, laminated sequence mainly determined by chemical energy liberated. In fact, often overlaps for uneven sediment or infauna disturbance—bioturbation.. (mainly in lake)

Various heterotrophic pathway (relative proportion) 380m marine sediment, negligible manganese(Mn) oxidation

Overview of benthic diagenesis processes

Redox state of seidments Oxidized in surface Reduced in deeper sediments Redox potential (Eh); degree of oxidations; high value means more oxidized No free electron!! Oxidation and reduction occurs at the same time

Vertical gradients in sediments Predictable sequence of respiratory chemical processes O2 ; 0 cm NO3 :0~4 cm SO42- ; CO2: RDL : redox discontinuity layer Competition between anaerobic processes Ability to get the OM or H2 Toxic end products; H2S

Energy flow in estuarine sediment Micro heterotrophic production ; O2+Non-O2  food for benthic organism Reduced chemicals  chemoautotrophic bacteria.

Diagenesis Diagenesis : overall transformation of particulate material Early diagenesis : upper sediments Diagenesis can be estimated by examining vertical profiles after time-depth relationship is established Studying the “liquid phase”(porewater) is better : large change due to diagenesis Change in products, Eh, pH, color Color (because of iron) Brown; iron oxide Grey : iron-sulfur compounds Balck: ferrous sulfide (FeS) pyrite (FsS2)