This study analyzed sediment samples from tidal creeks that flow into the Intracoastal Waterway in Wilmington, NC to determine concentrations of bioavailable trace metals. Sediment samples were extracted using 1M HCl and analyzed for concentrations of Ni, As, Cr, Co, Cu, Zn, Ag, Cd, and Pb. The study found relatively high concentrations of Zn and Cu in creek sediments that exceeded thresholds for potential toxicity to aquatic organisms. Depth analysis of sediment cores revealed increasing metal concentrations with depth in some creeks, possibly due to higher inorganic content, while other creeks showed decreasing metal concentrations with depth. The sources of elevated metals were attributed to inputs from anti-fouling boat paints

1. Trace Metals in Tidal Creek Sediments:
The Effects of Anthropogenic Inputs
Wilmington, NC
Brian Burkhardt
Department of Chemistry and Biochemistry
University of North Carolina Wilmington

2. Outline
Objectives
Background on Trace Elements and
Bioavailability
Methods
Results and Interpretation
Conclusions

3. Objectives
 To determine the bioavailable concentrations
of trace metals in various sediment samples
from creeks flowing into the Intracoastal
Waterway (Ni, As, Cr, Co, Cu, Zn, Ag, Cd, and
Pb)
 Depth analysis
 Evaluate concentrations and contamination

4. Background: Trace Metals
 Most metals are naturally present in the
environment
 Some metals are dominant in the inorganic
fraction of sediments (e.g., Al, Fe, Mn in clays)
 Some metals are essential for biological
processes (Fe, Zn, Cu)
 All metals are toxic at sufficiently high
concentrations.
Nadella et al. 2008

5. Sources of Trace Metals
 Chromated Copper Arsenate (CCA) on pressure-
treated lumber (Barraj et al. 2008)
 Cu and Zn have been added to antifouling paints
that are applied to boat hulls and submerged
structures (Singh et al. 2009; Nadella et al. 2009)
 Sewage spillages (Mallin et al. 2007).
 Increased development and runoff (e.g., Zn from
tire wear on roads) (Wang et al. 2002)

6. Background: Sediments
Sediments are known to be a sink for
contaminants including metals (Wang et al. 2002)
 Trends with time in metal
concentrations can be accurately
determined from down core data (Birch et al 1998;
Nolting et al. 1999; Valette-Silver 1993)

7. Background: Bioavailability
 Many factors contribute to the extent biota are
influenced by trace metals (i.e. feeding rates,
assimilation efficiencies, digestive characteristics,
salinity, etc.)
 Accumulation may vary between species
 Total metal concentrations do not give accurate
predictions of amounts affecting aquatic organisms.
 Using a single dilute acid extraction is a good indicator
of the bioavailable fraction.
Jackim et al. 1977; Alomary & Belhadj 2007; Sahuquillo et al. 2003; Wang et al. 1997; Mayer et al
1996; Luoma 1989; Tessier & Campbell 1987; Weimin et al. 1992

8. Study by Wiemin et al. 1992
 Metals accumulated in 3 marine invertebrates were
compared to the concentrations extracted with 1 N
HCl from the same sediment.
 Tissue concentrations in V. australis as a function of
HCl extractions shows a linear trend for Pb and an
exponential increase for Zn and Cd.

9. Sampling Sites Bradley Creek
Hewlett's Creek
Whiskey Creek
Bradley Creek
Hewletts Creek
Whiskey
Creek
BC 1
BC 2
BC 3
BC 4
BC 7
BC 8
AG 1
HC CORE
HC 1
HC 2
WC 1
WC 2
BC CORE

10. Methodology
 Obtain samples from within the top 2-3 cm of
sediment
 Cores were taken at two sites (BC and HC) and
sectioned at 2 cm intervals from 0-10 cm
 Freeze-dry samples and gently disaggregate
 Size-fractionated by sieving through 500 µm mesh
sieve
 Leach (1 g/20 mL) in 1 M HCl for 2 hours (with
shaking)
 Filter and dilute leachates
 ICP-OES analysis

11. Calibration Curve and Spectra

12. Comparative Trial
with SRM results
 1 M HCl leaches
fraction of total
concentration
 2 hour vs. 24 hour
nearly identical
 % varies with element
2 hours 24 hours
ug/g % Recovery ug/g % Recovery
Ni 11.3 ± 0.19 25.62% 11.29 ±0.38 25.60%
Co 4.52 ±.15 32.29% 4.14 ±.54 29.57%
Cd 2.65 ±.08 76.81% 2.7 ±.01 78.26%
Zn 248.2 56.67% 255.9 ±22.3 58.42%
Cu 64.32 65.23% 68.42 ±1.2 69.39%
0
50
100
150
200
250
300
350
400
450
500
Ni Co Cd Zn Cu
ug/g
1 M HCl leach Standard Reference Material

13. Surface sediment data
Interpret concentration significance
Establish trends in tidal creeks
Evaluate any potential toxicities

14. Trace Metal Concentrations found in Tidal Creek Sediments
 Relatively high concentrations of Zn and Cu
0
20
40
60
80
100
120
140
160
180
BC 1 BC 2 BC 3 BC 4 BC 7 BC 8 AG 1 HC 1 HC 2 WC 1 WC 2
Sampling Site
ppm (ug/g dry weight)
Cu
Pb
As
Zn
0
1
2
3
4
5
6
7
8
9
BC 1 BC 2 BC 3 BC 4 BC 7 BC 8 AG 1 HC 1 HC 2 WC 1 WC 2
Sampling Site
ppm (ug/g dry weight)
Cr
Ni
Co

15. Ag and Cd
Ag and Cd were below detection.
 Possible factors to consider:
 Metals are not found naturally in environment
 Distribution affected by forming sulfides

16. Concentration Trends
Hewlettt's Creek
Concentrations of Cu, As, Cr, and Zn in sediment from 1 M HCl
0
10
20
30
40
50
60
70
80
90
100
HC-1 A HC-1 B HC-2 A HC-2 B
Sampling Site
ppm
Cu
As
Cr
Zn
 Precision of study
Higher concentrations in upper branches

17. Concentration Trends
Whiskey Creek
Concentrations of Cu, As, Cr, and Zn in sediment from 1 M HCl
0
20
40
60
80
100
120
140
160
WC-1 A WC-1 B WC-2 A WC-2 B
Sampling Site
ppm
Cu
As
Cr
Zn

18. Fe, Al, and Mn
 These metals are important components of the inorganic
fraction of sediments (aluminosilicate clays) and are often used
in normalizing samples with respect to grain size.
0
1,000
2,000
3,000
4,000
5,000
6,000
7,000
8,000
9,000
10,000
BC 1 BC 2 BC 3 BC 4 BC 7 BC 8 AG 1 HC 1 HC 2 WC 1 WC 2
Sampling Site
ppm (ug/g) dry weight
Fe
Al
Mn

19. Association of trace metals with Al and Fe
y = 0.0003x + 0.2818
R = 0.823
p < 0.01
0
0.2
0.4
0.6
0.8
1
1.2
1.4
0 500 1000 1500 2000 2500 3000 3500 4000
Al (ppm)
Ni (ppm)
y = 0.0001x + 0.2864
R = 0.9114
p < 0.01
0
0.2
0.4
0.6
0.8
1
1.2
1.4
0 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000
Fe (ppm)
Ni (ppm)
Al and Fe trends Indicates
association with clays
 Zn, Cu, Pb, As, Ni, and
Co showed significant
correlations with Fe and Al.

20. Interpreting Data and Contamination
 Comparisons of similar studies with
contaminated and uncontaminated sediments
 Background concentrations
 Are these concentrations harmful?

21. Comparisons with Contaminated
and Uncontaminated Sediments
Low concentrations of Al, Cr, and Fe.
Higher concentration of Cu.
Al (%) Cr (µg/g) Cu (µg/g) Fe (%)
0.1 N HCl (Nolting et al. 1999) 0.05 ± 0.0 - 0.82 ± 0.12 0.06 ± 0.01
0.5 N HCl (Angelidis & Aloupi 2000) 0.288 ± 0.05 32.19 ± 5.6 17.43 ± 4.2 0.538 ± 0.064
0.5 M HCl (Sutherland 2002) 0.59 ± 0.16 - 52 ± 21 1.06 ± 0.34
1 M HCl 0.17 ± 0.08 5.099 ± 1.5 29.36 ± 18 0.47 ± 0.24

22. Mn (µg/g) Ni (µg/g) Pb (µg/g) Zn (µg/g)
0.1 N HCl (Nolting et al. 1999) 17.61 ± 1.03 n.d. 1.76 ± 0.3 4.45 ±.31
0.5 N HCl (Angelidis & Aloupi 2000) 272.5 ± 21.5 116.1 ± 40.5 17.15 ± 4.16 33.43 ± 7.5
0.5 M HCl (Sutherland 2002) 910 ± 380 47 ± 14 41 ± 34 142 ± 98
1 M HCl 743.7 ± 512.1 0.7871 ± 0.27 13.86 ± 8.0 97.77 ± 46.8
Comparisons with Contaminated and
Uncontaminated Sediments (cont.)
Low levels of Ni and Pb.
High concentrations of Zn and Mn.

23. Study by Apitz et al. 2009
Zn and Cu are above natural
background concentrations in Bradley
and Whiskey Creek.
Minimum Maximum Sites above range
Zn 40 130 BC 1, BC 2, BC 3, BC 4, WC 1
Cu 5 40 BC 1, BC 2, BC 3
Pb 5 50
Ni 5 45
As 5 35
Cr 5 80
Cd 0.1 1.2

24. Study by Bat and Raffaelli (1998)
 Metal toxicity on the amphipod Corophium volutator and the
polychaete Arenicola Marina
 Corophium LC50 values: 36.85 µg/g Cu and 31.87 µg/g Zn
 Arenicola LC50 values: 20 µg/g Cu and 50 µg/g Zn
 Every site sampled in this study exceeded these values for
Zn and Cu, but BC-7, HC-2, WC-2.
 No amphipods survived in sediment containing 99 µg/g Zn.
This study found 6 of the 11 sites sampled to be above this
concentration (BC-1, BC-2, BC-3, BC-4, BC-8, WC-1).

25. Core Data and Depth Analysis
Al
-10.0
-9.0
-8.0
-7.0
-6.0
-5.0
-4.0
-3.0
-2.0
-1.0
0.0
0 500 1000 1500 2000 2500 3000 3500
ppm (ug/g) dw
depth (cm)
Fe
-10.0
-9.0
-8.0
-7.0
-6.0
-5.0
-4.0
-3.0
-2.0
-1.0
0.0
0 200 400 600 800 1000 1200 1400 1600
ppm (ug/g) dw
depth (cm)
Bradley Creek
Hewletts Creek
Mn
-10.0
-9.0
-8.0
-7.0
-6.0
-5.0
-4.0
-3.0
-2.0
-1.0
0.0
0 100 200 300 400 500 600
ppm (ug/g) d/w
Depth (cm)
Pb
-10.0
-9.0
-8.0
-7.0
-6.0
-5.0
-4.0
-3.0
-2.0
-1.0
0.0
0.000 5.000 10.000 15.000 20.000 25.000 30.000
ppm (ug/g) dw
sediment depth (cm)

26. Core Data and Depth Analysis
As
-10.0
-9.0
-8.0
-7.0
-6.0
-5.0
-4.0
-3.0
-2.0
-1.0
0.0
0.000 1.000 2.000 3.000 4.000 5.000 6.000 7.000
ppm (ug/g) dw
sediment depth (cm)
Zn
-10.0
-9.0
-8.0
-7.0
-6.0
-5.0
-4.0
-3.0
-2.0
-1.0
0.0
0.00 10.00 20.00 30.00 40.00 50.00 60.00 70.00 80.00 90.00 100.00
ppm (ug/g) dw
sediment depth (cm)
Ni
-10.0
-9.0
-8.0
-7.0
-6.0
-5.0
-4.0
-3.0
-2.0
-1.0
0.0
0.000 0.100 0.200 0.300 0.400 0.500 0.600 0.700 0.800
ppm (ug/g) dry wt.
Sediment depth (cm)
Bradley Creek
Hewletts Creek
Cu
-10.0
-9.0
-8.0
-7.0
-6.0
-5.0
-4.0
-3.0
-2.0
-1.0
0.0
0.00 5.00 10.00 15.00 20.00 25.00
ppm (ug/g) dw
sediment depth (cm)

27. BC and HC Depth Analysis
 Bradley Creek:
 Sediment cores show high levels of Zn with depth.
 Cu decreases with depth, suggesting reduced
bioavailability
 Hewletts Creek:
 Trace metal concentrations show concentrations
tend to increase with depth.
 Likely due to high amount of vegetation at surface and
increasing inorganic fractions with depth

28. Conclusions
 Cu and Zn were found to be at potentially toxic levels in all
three tidal creeks
 Likely attributed to anti-fouling boat paints from marinas and road runoff.
 Upper branches of creeks have higher concentrations than
closer to estuary mouth
 Upper reaches of creeks likely have less flushing and finer sediments
 Further studies should be conducted in these areas to
establish total concentrations, organic carbon content, and
dating of depth sediments

29. Questions?
Special thanks to:
Dr. Stephen Skrabal
Dr. Ralph Mead
Dr. Larry Cahoon
Dr. Bart Jones
UNCW Honors Department
Funded by NC Sea Grant and Lower
Cape Fear River Program

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