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