Correlations Between Trace Metals in Sediments in Georgia

Jacquelyn Bracco4/27/2010

Why trace metals?

• Trace metal concentrations affected by natural and anthropogenic causes– Natural

• underlying geology of area• Weathering rates of rocks

in sediments

– Anthropogenic• Purification of metals• Dyes for textiles• Dumping of pollutants

• Going to look at correlations between:– Uranium (U) and Thorium

(Th)– Iron (Fe) and Manganese

(Mn)– Lanthanum (La) and

Cerium (Ce)– Uranium (U) and

Scanadium (Sc)– Titanium (Ti) and Hafnium

(Hf)

Geology of Georgia• Comparing correlations

across four distinct regions of Georgia1. Blue Ridge and Ridge and

Valley: mostly metamorphosed sedimentary rocks

2. Piedmont: granite, igneous and metamorphic rocks

3. Coastal Plain: Sedimentary Rocks

4. Shoreline: Very young sedimentary rocks

Image taken from USGS

1

2

3 4

Data Set• Data taken from the

National Uranium Resource Evaluation Hydrogeochemical and Stream Sediment Reconnaissance Program (NURE)

• Each data set (except for the shore) had over 2000 sample sites

• Samples taken from streams

Uraninite, an ore of uranium

Image taken from mindat.org

• All p values fell below 0.05, so correlations are statistically significant

U vs Th Fe vs Mn Ce vs La U vs Sc Ti vsHfNorth Georgia 0.85 0.51 0.98 0.09 0.33Piedmont 0.90 0.57 0.97 0.03 0.29Coastal Plain 0.95 0.50 0.89 0.21 0.60Shore 0.96 0.33 0.95 0.21 0.72

Pearson Correlation Coefficents

• High Correlations: abs(r) > .5• Medium: .5 > abs(r) > .3• Low: .3 > abs(r)

• All p values fell below 0.05, so correlations are statistically significant

Bootstrap Correlation Coefficients

• High Correlations: abs(r) > .5• Medium: .5 > abs(r) > .3• Low: .3 > abs(r)

U vs Th Fe vs Mn Ce vs La U vs Sc Ti vsHfNorth Georgia 0.86 0.52 0.98 0.09 0.34Piedmont 0.90 0.57 0.97 0.03 0.31Coastal Plain 0.95 0.50 0.89 0.21 0.61Shore 0.96 0.33 0.95 0.21 0.73

• None of the data was:•Normally Distributed (Chi- square test)•Or Statistically Equivalent (F test)

Bootstrap Regression• Calculated using

bootstrp with the polyfit option

• Example regressions for Piedmont region of Georgia 0 50 100 150 200 250 300 350 400 450

0

10

20

30

40

50

60

70

80

90

100U vs Sc

Sc

U

0 2 4 6 8 10 12 14 16 18

x 104

0

500

1000

1500

2000

2500

3000

3500

4000

4500

5000Ti vs Hf

Hf

Ti

0 50 100 150 200 250 300 350 400 450-500

0

500

1000

1500

2000

2500U vs Th

Th

U0 10 20 30 40 50 60

0

0.5

1

1.5

2

2.5x 10

4 Fe vs Mn

Mn

Fe0 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000

0

1000

2000

3000

4000

5000

6000Ce vs La

La

Ce

Conclusion

• Correlations vary over geologic region– Possibly related to

geology

• Uranium and thorium, cereium and lanthanum had high correlations for all regions