evolution of the source of storm particulate organic
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Evolution of the source of storm particulate organicmatter exported along forested nested catchment. ?
Impact of granulometry and climateLaurent Jeanneau, Richard Rowland, Shreeram Inamdar
To cite this version:Laurent Jeanneau, Richard Rowland, Shreeram Inamdar. Evolution of the source of storm particulateorganic matter exported along forested nested catchment. ? Impact of granulometry and climate. Eu-ropean Geosciences Union General Assembly 2016, Apr 2016, Vienne, Austria. Geophysical ResearchAbstracts, 18, pp.EGU2016-6097, 2016. �insu-01309196�
Laurent JEANNEAU1, Richard D. ROWLAND2 and Shreeram INAMDAR2
1. Géosciences Rennes, CNRS-Université de Rennes 1, France; 2. Plant and Soil Sciences, University of Delaware, Newark, DE, USA
Discussions and message to carry back • In the 12Ha catchment, the POM mainly derived from litter, wetland A and forest O horizons. Their relative contributions changed along the particles size continuum and from one event to another. • At the scale of the headwater catchment, the sources of POM changed with an increasing proportion of stream bed-derived POM downstream. Going downstream seems to decrease the differences along the particles size continuum. • The composition of POC changed along the particle size continuum: different fractions from different sources. • Investigation at the molecular scale using THM-GC-MS seems to provide fruitful data to determine the sources of POM transferred along nested catchments.
Investigation at the molecular scale Thermally assisted hydrolysis and methylation
Macromolecules lysis
Step 1: Thermochemolysis
Step 2: Gas chromatography
Separation
Step 3: Mass spectrometry
Identification
O H
O H CO2H
CO2H
OH HO O
HO OH
OH
Freeze-dried POM
0
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30
40
0
40
80
120
May 1, 2014
April 21, 2015
July 1, 2015
Sept 30, 2015
Rai
nfa
ll (m
m)
Total Rainfall
Max hourly I
Med hourly I
0
50
100
150
200
0
2
4
6
Max runoff
Max discharge
Hydrological data
Ho
url
y In
ten
sity
(m
m/h
r)
Max
Dis
char
ge
(L/s
) M
ax T
urb
idit
y (U
T)
Max
Su
spe
nd
ed
M
atte
r (g
/L)
No
dat
a
Max
Ru
no
ff
(mm
/hr)
Sampling area Fair Hill Watershed site • Piedmont region of Maryland, USA • Cold-temperate climate • Annual rainfall: 1007 (2014), 1165 (2015) mm • Elevations from 48 to 116 m (89 ± 14 m; mean ± SD) • Slopes from 0 to 35% (7.4 ± 5.0 %; mean ± SD)
Nested catchment 12 and 79 Ha
Sampling of deposited sediment during 4 storm events
Sampling of potential end-members
Outlet of the 12 Ha catchment
Deposited sediment sampler
0
25
50
75
100
Fine (<250µm)
Medium Coarse (>1mm)
May 01, 2014
Apr 21, 2015
Jul 01, 2015
Sep 30, 2015
May 01, 2014
Apr 21, 2015
Jul 01, 2015
Sep 30, 2015
12 Ha 79 Ha
Distribution of particles size End-members Wetland Stream bank A & B Stream bed Upland A Forest O & Litter
Results of the molecular analysis
Event 1
Event 2
Event 3
Event 4
1. First PCA treatment based on the distribution of the type of molecules Individuals: End-members Variables: % of fatty acids (FA), carbohydrates (CAR), phenols (PHE) among the analyzed compounds and the sum of the area per gram of analyzed sample.
2. Second PCA treatment based on the distribution of plant-derived markers Individuals: End-members
Variables: Relative proportion of the eight most abundant PHE and plant-derived FA.
1C
1M
1F
2C
2M
2F
3C
3M 3F
4F
4M
4C
C
M
F
1C
1M
1F
2C
2M
2F
3C 3M
3F
4F
4M
C
M
F
Seco
nd
co
mp
on
en
t (2
6.4
%)
First component (66.7 %)
A
B
O
Li
Forest floor Upland A Wetland Stream Bank Stream bed
nX n: event number X: C, coarse; M, medium; F: fine
Orange: 12 Ha catchment Blue: 79 Ha catchment
1C
1M 1F
2C
2M 2F
3C
3M
3F
4F
4M
4C
C
M
F
1C 1M
1F
2C 2M
2F
3C
3M
3F
4F
4M
C
M F
Seco
nd
co
mp
on
en
t (3
2.2
%)
First component (40.0 %)
nX n: event number X: C, coarse; M, medium; F: fine
Forest floor Upland A Wetland Stream Bank Stream bed
Orange: 12 Ha catchment Blue: 79 Ha catchment
A
B
O
Li
Differentiation between the potential end-members. Specific areas are
increased by spatial heterogeneity.
The composition of POM changed along:
(1) the catchment (differentiation between the samples from the 12 Ha
and the 79 Ha catchments), (2) the size continuum from coarse to fine fractions
and (3) the year.
The 12 Ha catchment POM derived mainly from a combination of Litter,
Forest O and Wetland A horizons. The contribution of stream bed increased
downstream.
% CAR
% FA
% PHE
[Sq]
FA
PHE
Context and question Particulate Organic Matter (POM) plays a key-role toward biodiversity, ecotoxicology and within the C cycle. POM exported within the fluvial suspended matter load during storm events may represent up to 80% of its annual load. 1. Where does this POM come from?
2. Is it homogeneous along the particle size continuum?
3. How its source may change down a continuum of catchment drainage locations?
4. Is there a seasonal effect?
Acknowledgments This work benefits from NSF and USDA funding (grant numbers IIA-1330238 and 2015-37020-23585, respectively). Contact: [email protected]
12 Ha
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8 Susp Sed
Turbidity
12 Ha