1. 하구및 연안생태Coastal management
2015 년 가을학기

2. 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”

3. 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

4. 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

5. 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

6. 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

7. 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

8. Aerobic respiration
C6H12O6 + 6O CO2 + 6H2O E

9. Quantifications oxidation of glucose (C6H12O6)
C6H12O6 + 6O2 ---> 6CO2 +6H2O
276 g g g 108g
1g g g g

10. C6H12O6 + 6O2 ---> 6CO2 +6H2O
276 g g g 108g
발열량: ( )-217=675 kcal
1g g g g
발열량: 675/276 = 2.44 kcal=2440 cal
1g C의 에너지
2440 x 276/72=9.353kcal

11. 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

12. 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)

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

14. Overview of benthic diagenesis processes

15. 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

16. 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

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

18. 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)