1. Sediment in Lake Soyang, South Korea
: as Integrating Archive of Catchment Processes and Potential Effect on Lake Water Quality and Methane Gas Ebullition
Kim, Kiyong1, Kim, Bomchul2, Knorr, Klaus-Holger3, and Stefan, Peiffer1
1Department of Hydrology, University of Bayrueth, Bayreuth, Germany
2Department of Environmental Science, Kangwon National University, Chuncheon, Korea
3Institute for Landscape Ecology, University of Muenster, Muenster, Germany
Photo of Lake Soyang

2. Background Lake Water Quality Impact on Land use changes
Lake Sediment Formation
Watershed Activities
Monsoon Climate Effect
Land use changes
Causing runoff
Tillage
Flushing effect
Fertilizer overuse
Impact on
Lake Water Quality

3. Background
Sediment controls lake water quality under certain condition in monsoon climate area

4. Study Site – Lake Soyang
Agricultural area, Heaan
dendrictic shape
Metropolitan city, Seoul
(Map source and lake inforamtion : Bomchul Kim et al., 2001 & Jai-Ku Kim et al., 2007)

5. Sampling Location and Frequency
Samples
Sampling time
Lake water
Every month
By depth
Stream water
Inflow streams
Lake sediment
Before & after monsoon season
Core & grab samples
Gas sample
Before monsoon
Bubble type in water

6. Results – Precipitation in Watershed
Gentle summer monsoon climate
Intensive summer monsoon climate
100mm/day
(Source : www. wamis.go.kr)

7. High amount of nutrients and OMs
Results – Lake Water
Oxygen depletion in hypolimnion with thermal stratification in summer
Mixing period in winter season
High amount of nutrients and OMs
Oxygen depletion
in bottom water

8. Results – ORP, pH and DIP pH, ORP and DIP Sediment Porewater
ORP : -130 ~ -80mV
Under this conditions, the concentration of Fe(II) and Mn(II) rises and, further sulfate begins to be reduced
The phosphate concentration in the porewater was higher in top sediment than bottom water layer

9. Results – Lake Water
Detached Fe from Lake Soyang watershed transport to the lake water body especially during summer monsoon season after intensive rainfall event

10. Results – Lake Water
Mn concentration in bottom water layer is the highest during summer monsoon season as same as Fe
Mn and Fe can be used as electron acceptors faster than sulfate reduction
(Robert G. Wetzel, 2001)

11. Results – Porewater 2012. Sep. 2012. June
In sediments, Fe oxides are reduced by two mechanisms:
(1) microbial dissimilatory Fe reduction as terminal electron acceptors in respiration
(2) chemically by sulfides formed in microbial sulfate reduction
(Canfield et al., 2005; Lovley, 1991)

12. Results – Sediment
We thought high amount of pyrite (Fe2S2) is deposited after sulfate reduction process

13. Results – Gas ebullition
Buoy
(Jari T. Huttunen et al., 2001)
Gas bubble sampler

14. Results – Gas ebullition
Site
Total gas volume
(ml hour-1)
Ebullition
(g C m -2 yr -1) 1
7.5
16.19 2
416.7 3
6.7
8.63 4
15.0
29.08
Source
Lake
Area
(ha)
Ebullition
(mg C m -2 yr -1)
Bastviken et al., 2004
Brown
32.9
1428
Crampton
25.8
841
East Long
2.3
2649
Hummingbird
0.8
1152
Morris
5.9
16284
North Gate
0.3
896
Paul
1.7
2680
Roach
45.0
4452
Huttunen et al., 2003
Postilampi
3.0
6750
Tuesday
407.0
983
Casper et al., 2004
Ward
1.0
54312

15. Conclusions
Fe, Mn input from watershed to Lake Soyang control phosphate release from sediment into water layer .
Significant amount of methane emission occurs from the lake into atmosphere in the form of ebullition
Intensive and well-organized field work is required for elucidating lake bottom sediment processes

16. Thanks to … TERRECO project and people
University of Bayreuth, Hydrology department people
Kangwon National University, Prof. Bomchul Kim and Environmental Ecology laboratory people

17. Thank you for your attention