Item #1
Trace element loads in
urbanized watersheds and the
potential for treatment of
NPS loads
Lester McKee
Sources Pathways and Loadings Workgroup
May 22nd 2007
San Francisco Estuary Institute
1
Item #1
History
2000 – 2002: Study design and location developed
and recommended by SPLWG
WY 2003:
CEP ($150k)
WY 2004:
RMP and CEP ($50k+75k)
WY 2005:
RMP, USACE/SCVWD, SCVURPPP
($50k + $100k + $23k)
San Francisco Estuary Institute
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Impetus

May 15th 2006 WG meeting.



Members asked about the trace metals data for Guadalupe and remarked
they did not remember it being reported – Lester responded that there
was three years of data and that we only reported it once (year 2).
Mike C asked what inter-annual variability might look like for
contaminants other than Hg. Lester said that he thinks the Hg in the
Guadalupe River would be more variable than sediment but he cannot say
for other metals or the organics. Mike suggests that Lester do the analysis
for the others. WG agreed it would be informative.
Nov 13th WG meeting.

“Try to write future reports so that there is a better connection to
management alternatives as an endpoint”
San Francisco Estuary Institute
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Item #1
Sampling Location

Area: 414 km2

4th largest watershed (8.4%)

178 km2, upstream from reservoirs
leaving 236 km2 of which >78% is urban
land use

Population: 486,500 (7.2% of Bay Area)

Highest elevation: Loma Prieta (1,155 m)

Precipitation varies from 300-1,100mm
and falls during winter (Nov-April: 89%)

Annual Q: 0.42-241 Mm3 or
approximately 1-640mm
San Francisco Estuary Institute
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Item #1
Sampling Methods

USGS flow gage 11169025 at Hwy 101
adjacent to SJ Airport

Sampling based on hypothesis that SSC is a
surrogate for predicting TE concentrations

FTS Ltd. DTS 12 turbidity probe with wiper

Water samples collected using D74 or DH48
and analyzed for SSC and GS

LOESS regression used to generate
continuous 15-minute SSC

Water samples collected during floods using
D95 and analyzed for total Ag, As, Cd, Cr,
Cu, Ni, Pb, and Zn
San Francisco Estuary Institute
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QA/QC



All samples run through the RMP QA/QC program
2, 3. Silver concentrations in these batches
were considered marginally acceptable as the
matrix spike and duplicate recoveries were within the data quality objectives.
4. These samples were not rejected because the matrix spike and duplicate recoveries
were within the data quality objectives and more importantly they were not anomalous
with respect to SSC
San Francisco Estuary Institute 6
Item #1
Loads Estimation

Linear interpolation when storms are well samples

Stratified regression estimator during other storms depending on
the predominant source of runoff based on rainfall and runoff
gauging information from further up the watershed:

Used “lower watershed urban” regression when water from there

Used “upper watershed non-urban” regression when water from there

Base flow: used upper watershed regression but choice made little
difference to the annual loads estimation
San Francisco Estuary Institute
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Item #1
Error Analysis

Errors accounted for during loads estimation
were:
 flow (10%)
 SSC (2%)
 SSC-Turbidity regressions (2%)
 Interpolation / SSC-trace element
specific regressions:





Ag: 23%
As: 31%
Cd: 13%
Cr: 13%




Cu: 10%
Ni: 13%
Pb: 7%
Zn: 14%



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

Ag: 46%
As: 4.9%
Cd: 13%
Cr: 7.3%




Cu: 4.3%
Ni: 6.2%
Pb: 3.6%
Zn: 2.3%
The total estimated errors for loads
calculations were:



The mean coefficient of variation (CV)
of duplicate field samples was:



We did not include an error for
variation in the cross section because
this was accounted for within the USGS
SSC records
SSC: 10%
Ag: 52%
As: 33%
Cd: 21%
Cr: 18%




Cu: 15%
Ni: 17%
Pb: 13%
Zn: 17%
Note, that we have found no other papers
that have quantified errors in loads
calculations, yet clearly, claims of loads
variation between years may not be valid
San Francisco Estuary Institute
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Item #1
Results – Precipitation and Runoff

30-year average (July 1st, 1976 - June
30th, 2005): 388 mm and a coefficient of
variation (CV) of 0.39



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
WY 2003: 100%
WY 2004: 90%
WY 2005: 164%
WY 2006: 150%
Storms were generally of low magnitude
and duration with the exception of five
storms (December 19th 2002; November
9th 2003; December 21st, 2003;
December 27th, 2004; October 26th,
2004)
Runoff similar (MAR = 57.4 Mm3):




WY 2003: 106%
WY 2004: 92%
WY 2005: 128%
WY 2006: 221%
San Francisco Estuary Institute
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Results – Concentration Statistics
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Results – Concentration Scatter Plots
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Item #1
Results – Concentrations
San Francisco Estuary Institute
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Correlation Analysis
As
Cd
Cr
Cu
Ni
Cd
0.49**
Cr
0.01
-0.04
Cu
0.33*
0.80**
0.08
Ni
0.01
-0.07
0.91**
0.02
Pb
0.30*
0.79**
0.04
0.83**
-0.05
Zn
0.39*
0.84**
0.06
0.91**
-0.03
*p<0.01
**p<0.001
Pb
1
1
1
1
1
0.93**
Groups:
1. Ag
2. As
3. Pb, Zn, Cd, Cu
4. Cr, Ni
San Francisco Estuary Institute
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Item #1
Daily Loads
San Francisco Estuary Institute
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Annual
Wet
Season
Loads
San Francisco Estuary Institute
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Guadalupe versus the World
(Peer-reviewed Literature)
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Ag – Hardly ever reported, Guadalupe similar
As – Reported previously in 9 urban watersheds, Guadalupe similar
Cd – Reported previously in 19 urban watersheds, Guadalupe similar – but
time trend in world literature
Cr – Reported previously in 29 urban watersheds, Guadalupe greater except 2
industrial watersheds
Cu – Reported previously in 34 urban watersheds, Guadalupe similar
Ni – Reported previously in 20 urban watersheds, Guadalupe greater except 1
industrial watershed and 1 high density residential watershed – but time trend
evident
Pb – Reported previously in 39 urban watersheds, Guadalupe similar – but
time trend in world literature
Zn – Reported previously in 29 urban watersheds, Guadalupe similar
San Francisco Estuary Institute
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Item #1
Cadmium
1000
Cd (µg/L)
100
10
2
R = 0.0269
1
0.1
R2 = 0.0069
0.01
0.001
0.01
0.1
1
10
100
1000
2
Area (km )
1000
Cd (µg/L)
100
10
2
R = 0.4154
1
0.1
2
R = 0.4762
0.01
1970
1975
1980
1985
1990
1995
2000
2005
2010
Year
San Francisco Estuary Institute
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Item #1
Chromium
10000
Cr (µg/L)
1000
R2 = 0.0629
100
10
1
R2 = 0.3359
0.1
0.001
0.01
0.1
1
10
100
1000
2
Area (km )
Guadalupe
10000
Cr (µg/L)
1000
R2 = 0.0619
100
10
R2 = 0.0022
1
0.1
1970
1975
1980
1985
1990
1995
2000
2005
2010
Year
San Francisco Estuary Institute
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Item #1
Nickel
1000
Ni (µg/L)
100
R2 = 0.0954
10
R2 = 0.2802
1
0.1
0.01
0.1
1
10
100
1000
Area (km 2)
Guadalupe
1000
Ni (µg/L)
100
R2 = 0.3918
10
R2 = 0.0006
1
0.1
1970
1975
1980
1985
1990
1995
2000
2005
2010
Year
San Francisco Estuary Institute
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Item #1
Lead
100000
Pb (µg/L)
10000
1000
R2 = 0.0298
100
10
R2 = 0.1528
1
0.1
0.001
0.01
0.1
1
10
100
1000
Area (km 2)
Lee and Bang, 2000 – Korea
Choe et al., 2002
Buffleben et al., 2002
100000
Pb (µg/L)
10000
1000
100
R2 = 0.459
10
R2 = 0.1454
1
0.1
0.01
1965
1970
1975
1980
1985
1990
1995
2000
2005
2010
Year
San Francisco Estuary Institute
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Item #1
Mahler et al., 2006. Trends in metals in urban
and reference lake sediments across the
United States, 1970-2001 (ET&C 25, 1698-1709)




Cd decreased by 29%
Cr decreased by 15%
Ni decreased by 22%
Pb decreased by 46%
San Francisco Estuary Institute
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Item #1
Treatment
Potential?
A.
B.
C.
D.
1st storm only
1st storm and largest flood
All rising stage
Peak shaving
San Francisco Estuary Institute
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