McKee and Gilbreath, 2015.
CONCENTRATIONS AND LOADS OF SUSPENDED SEDIMENT AND TRACE ELEMENT POLLUTANTS
IN A SMALL SEMI-ARID URBAN TRIBUTARY, SAN FRANCISCO BAY, CALIFORNIA
Lester J. McKeea* and Alicia N. Gilbreatha
a San
Francisco Estuary Institute, 4911 Central Avenue, Richmond CA 94804, USA
* Corresponding author: lester@sfei.org; phone 510-746-7363; Fax 510-746-7300
Supplementary Section
Figure S1. Relationships between turbidity and trace element concentrations and suspended
sediment concentrations (SSC) illustrating correlation lines (or the lack thereof) and the 95%
confidence interval. Note the outliners represented by the triangle symbols were not used in the
regression equations used to loads estimation. The outliers were from the same four samples for
nickel and chromium. A thorough quality check did not reveal any reason to reject these data.
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McKee and Gilbreath, 2015.
Figure S2. Relationships between flow and trace element concentrations and suspended sediment
concentrations (SSC) illustrating the lack of a strong correlation in most cases and the 95%
confidence interval.
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McKee and Gilbreath, 2015.
Table S1. The coefficient of determination and p-values for linear regression relationships
between analytes and flow and turbidity. This illustrates the value of using turbidity as a
surrogate measurement for most trace elements that are dominantly transported in particulate
phase. It also demonstrates that flow, in most cases, is a poor predictor of concentration. The use
of the turbidity surrogate method addresses the key challenge of collecting representative
samples during short lived high flow conditions in arid-climate systems. The results demonstrate
the use of a surrogate measurement that can easily and reliably be logged at short time intervals
and used to estimate concentrations during critical peak flows. These estimate couple with flow
measurements at the same time interval can be used to compute reliable loads estimates that can
be summed to any other time interval desired (hourly, storm, weekly, monthly, or annual).
Flow
Analyte
Turbidity
p-value
r²
Aluminum
r²
0.42
0.0016
0.94
p-value
<0.0001
Cadmium
0.45
0.0009
0.86
<0.0001
Chromium
0.63
0.0001
0.87
<0.0001
Copper
0.02
0.3939
0.86
<0.0001
Iron
0.03
0.5826
0.97
<0.0001
Lead
0.53
0.0002
0.87
<0.0001
Nickel
0.44
0.0039
0.59
<0.0001
Silver
0.37
0.0002
0.74
<0.0001
Zinc
0.46
0.0007
0.87
<0.0001
HgT
0.05
0.75
<0.0001
SSC
0.08
0.0362
<0.0001
0.84
<0.0001
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