Upload
kelley-beasley
View
217
Download
1
Embed Size (px)
Citation preview
Dissolved Organic Carbon Concentration and Fluorescence Characterization of Tempe Town Lake
By Marissa Raleigh
Tempe Town Lake Background• Man-made lake built in the Salt River channel• Held in by inflatable dams• Designed for both flood control and recreation• The largest loss is through evaporation, major input is precipitation
http://4.bp.blogspot.com/-EjQ_SIBPSxo/ULjJm43TfCI/AAAAAAAAC0g/b8LOPO88qfY/s1600/tempe+town+lake+aerial.jpg
0.5 miles
Fluorescence
DOCMethodsSampling• Twice a week• After Rain events
Measurements:• pH• Temperature• Conductivity• Dissolved Oxygen• Dissolved Organic Carbon
(DOC)• Fluorescence
An excitation-emission matrix (EEM) is produced
Fluorescence occurs when an excited electron relaxes to its ground state by emitting a photon
What is Fluorescence?
Fluorescence is a method used to look at the composition of DOC
Dissolved Organic CarbonDissolved Organic Carbon
Sample Date
Sep'12 Jan'13
May'13 Sep'13
Jan'14
DO
C (
mg
/L)
2
3
4
5
6
7
Pre
cipi
tatio
n (in
.)
0.0
0.5
1.0
1.5
2.0
Tem
pera
ture
(de
g C
)
0
20
40
60
80
100
DOC (mg/L)Precipitation (in.)Temperature (deg C)
• Overall seasonal pattern w/higher concentrations in Fall/Spring
• Concentrations increase w/rain events
Fluorescence Sum
Sample Date
Sep'12 Jan'13
May'13 Sep'13
Jan'14
Flu
ores
cenc
e S
um
0.1
0.2
0.3
0.4
0.5
Pre
cipi
tatio
n (in
.)
0.0
0.5
1.0
1.5
2.0
Fluorescence Sum
• Measure of total fluorescence intensity
• Rain events bring in fluorescent material
• Overall pattern is different from DOC
Data
Freshness Index• Indicates the proportion of recently
produced DOC• The ‘freshness’ is generally high,
indicating much of the DOC in Tempe Town Lake is “recently produced”, most likely by algae
• Decreases after rain events suggest run-off has ‘older’ organic matter
Fluorescence Index (FI)• Higher values (>1.5) reflect
microbially-derived DOC; Lower values reflect terrestrially-derived DOC
• Tempe Town Lake is highly microbial• Rain events bring in DOM different
from what is currently in the lake
Fluorescence Index
Sample Date
Flu
ores
cenc
e In
dex
1.45
1.50
1.55
1.60
1.65
1.70
Pre
cipi
tatio
n (in
.)
0.0
0.5
1.0
1.5
2.0
Freshness
Sample Date
Sep'12 Jan'13
May'13 Sep'13
Jan'14
Fre
shne
ss
0.80
0.82
0.84
0.86
0.88
0.90
0.92
0.94
Pre
cipi
tatio
n (in
.)
0.0
0.5
1.0
1.5
2.0
Summary
• Dissolved organic carbon concentrations [DOC] vary both seasonally and with precipitation
• Total fluorescence changes mainly with precipitation
• Precipitation brings in material that is different from what is presently in the lake at the time of sampling
• Hilairy Hartnett• Zach Smith, Maggie Bowman, and the entire
CaNDy Lab group• Funding from ASU/NASA Space Grant and NSF
CAREER #0846188
Acknowledgements