using chemistry to determine sediment source in white clay creek white clay wild and scenic...
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Using Chemistry to Determine Sediment Source in White Clay Creek
White Clay Wild and Scenic Watershed SummitSeptember 25, 2012
Dr. Diana L. Karwan
University of Delaware Department of Geological SciencesStroud Water Research Center
Photo: Marissa Morton
Research Questions
Christina River Basin CZO:What is the net carbon source or sink provided by the Christina River
Watershed?
My Research:
1.What is the composition and source of suspended material in White Clay
Creek?
2.Does eroded mineral material stabilize and transport organic carbon in the
fluvial network?
3.(How) does the fluvial transport of suspended material differ based on its
composition on seasonal and storm time scales?
(www.udel.edu/czo)
Photo: Marissa Morton
Research Questions
What is the composition and source of suspended material in White Clay Creek?
Photo: Marissa Morton
Approach
Sediment Fingerprinting – possible sources
Rill Erosion
Channel Banks(legacy sediments + buried
soil horizons, higher Fe)
Trail Crossing(animal evidence???)
Road Dust(high Zn)
Overland Flow(surface soil: high 7Be, C&N
reflect plant community)
Photo: Marissa Morton
Study Area
Bran
dyw
ine R.
Red
Clay C
k.
White Clay Ck.
Christina R.
White Clay Creek:
•Total area: 277 km2
•Wild and Scenic River for entire watershed
•Urban, agriculture, and forest land use
•Drinking water supply in areas of PA and DE
Christina River Basin:
•Total area: 1440 km2
•3 main tributaries – Brandywine River, Red
Clay Creek, White Clay Creek
•Urban, agriculture, and forest land use
•Sediment TMDL
Photo: Marissa Morton
ApproachSediment Fingerprinting1.Field collection of suspended materials, landscape materials, precipitation2.Analyze for several chemical signatures3.Use data in a statistical model to determine fraction of stream material from various sources
Particulate Analyses:•Fallout radionuclides (7Be, 137Cs, 210Pb) •C, N, stable isotopes•Mineral surface area•Grain size•Mineral content (elemental and composition)• Microbial community characterization (16S,
rRNA, PCR, ITS-DGGE, sequencing)•FTIR•Separate colloids quantification
Streamwater Chemistry:•TSS•DOC•Anions + Cations•Others?
Photo: Marissa Morton
Approach
Field Collection Precipitation for Radioisotopes
7Be7Be
7Be7Be
Radionuclide Fingerprints
•Precipitation delivered
•Strong particle surface affinity
•All radioactive, so primary method of ‘disappearance’ is decay.
•Plant interception not well known (recent source < 30%)
•Erosion tracers:
Beryllium-7 (54 days)
Lead-210 (22 years)
Cesium-137 (30 years)
Beryllium-10 (1.3 million years)
Photo: Marissa Morton
Approach
Field Collection of Precipitation
Open Precipitation Stemflow
Canopy Throughfall
Photo: Marissa Morton
Approach
Field Collection!
Challenge: collecting enough solid material for all analyses during baseflow and storms
Photo: Marissa Morton
ISCO automatic sampler for 1 L streamwater samples
Pressure transducer for water height
55 gallon barrel and cell-phone-triggered submersible pump for suspended sediment
Approach
Field Collection!
The “Dial-a-Pump”
55 gal.barrel
55 gal.barrel
float switchturns off pump
Cell phone
open sourceelectronics(Arduino)
submersible pump
12V marine battery
Photo: Marissa Morton
Approach
Field Collection!
The “Dial-a-Pump”Scaled Up: 3 barrels
Photo: Marissa Morton
ApproachSediment fingerprinting at nested sites in White Clay Creek
Field Collection – Locations
5th order – Newark DE
3rd order – Avondale PA
1st order – Avondale PA
• No significant difference in concentration per event with canopy when examining a year of data
Results - Rainfall
TreesLeaves
No TreesSummer
No TreesWinter
TreesNo Leaves
Results – Shallow Soil
• Similar 7Be (short lived!) profile in open and forested area• Longer-lived 137Cs shows mixture that occurs in ‘plow layer’• Signatures of these isotopes in the stream might help tell us about the depth from which
erosion and sediment delivery occur
Preliminary Results – Source /Suspended Variations
Photo: Marissa Morton
Preliminary ResultsSuspended Material – Storm Collections
Storm collections began 9/30/2010•1 large sediment sample per storm•Target peak •For example: 25 February 2011
Photo: Marissa Morton
Preliminary ResultsSuspended Material – Storm Collections
Differences noted along storm hydrograph, beginning in April 2011
Photo: Marissa Morton
Preliminary ResultsSuspended Material – Storm Collections
August 25 – September 12, 2011
Hurricane Irene
Tropical StormLee
66 metric tonssediment export
135 metric tonssediment export
54 metric tons In peak event
Preliminary ResultsSuspended Material – Storm Collections
Preliminary Results – Radioisotope Fingerprinting
•7Be on stream sediment varies between seasons, with higher values in the spring and summer, and within single storms, with higher values generally earlier in a single event.
•One year of rainfall data does not show significant differences across seasons or in the presence or absence of a tree canopy.
•Does this mean the differences seen in stream material are from differences in erosion and delivery??????
soil A horizon,
river & coastal sediment
desert soil, B-C
horizon
deep ocean sediment
O hor
izon,
sedim
ent u
nder
anox
ic wat
er
leaf
litt
er,
alga
e
Mineral Surface Area (m2/g)0 20 40 60 80 100
Org
anic
car
bo
n (
%)
0
2
4
6
8
10
36
5249107
3301100
13973
26
<1
<1
<1
<1
2932
White Clay Creek POM with published sediment values
POM from White Clay Creek
Larger, temperate rivers (data from Keil et al. 1997, Mayer et al. 1994, Onstad et al. 2000)
Rivers draining deserts
Oxygen exposure times for marine sediments on the Washington shelf & slope and suboxic Mexican margin (data from Hartnett et al. 1998, Hedges et al. 1999, Keil et al. 2004)
<1
Preliminary Results
Preliminary Results - POM
•POM from White Clay Creek is relatively high in organic carbon content.• Organic carbon to surface area ratios closely resemble the surface soil
from the land cover types in the catchment – agriculture and forest.
•OC and mineral surface area change with season, but their ratio remains constant and characteristic of relatively ‘fresh’ material.
Jim PizzutoDel Levia
Adam PearsonElyse Williamson
Rolf AatloJulia Marquard
Anthony Aufdenkampe Steve Hicks
Dave MontgomeryStephanie Dix
Acknowledgements
CRB CZO work was funded by the National Science Foundation [NSF EAR 0724971]
SSH CZO work funded by an NSF EAR Postdoctoral Fellowship[NSF EAR 1144760]
Denis NewboldSara Geleskie
Fred ShawErika Vazquez