Metal Deposition in Baldcypress Tree Rings:

Nickel, Copper, Chromium, Manganese and Iron

Margaret S. Devall1, Leonard B. Thien2, and George C. Flowers2

1USDA Forest Service, Center for Bottomland Hardwoods Research, P.O. Box 227, Stoneville, MS

2Tulane University, New Orleans, LA

Methods

• Cypress trees cored along bayou and reference area and chronology developed

• 5-year increments ground and pressed into pellets

• X-ray fluorescent spectrometer used to analyze samples

• Concentrations presented in spatial and temporal dimensions

Results

• First, levels of metals presented with respect to proximity to point source

• Second, history of pollution documented

NICKEL

0

2

4

6

8

10

12

14

0-10

10--2

0

20-3

0

40-5

0

50-6

0

80-9

0

100-

110

120-

130

130-

140

140-

150

150-

160

BAYOU STATIONS

PPM

Mean level of Ni is 6.6 at Stations 0-60 and 4.5 at Stations 80-160.

NICKEL CONCENTRATION IN BALDCYPRESS FROM BAYOU TREPAGNIER AND STINKING BAYOU

0

2

4

6

8

10

12

14

16

1905

1910

1915

1920

1925

1930

1935

1940

1945

1950

1955

1960

1965

1970

1975

1980

1985

1990

1995

TREE RING YEARS

PPM

BT/Ni

SB/Ni

COPPER

0

0.5

1

1.5

2

2.5

3

3.5

40-

10

10--2

0

20-3

0

40-5

0

50-6

0

80-9

0

100-

110

120-

130

130-

140

140-

150

150-

160

BAYOU STATIONS

PPM

Mean level of Cu is 2.4 at Stations 0-60 and 2.8 at Stations 80-160.

COPPER CONCENTRATION IN BALDCYPRESS FROM BAYOU TREPAGNIER AND STINKING BAYOU

0

2

4

6

8

10

12

14

1905

1910

1915

1920

1925

1930

1935

1940

1945

1950

1955

1960

1965

1970

1975

1980

1985

1990

1995

TREE RING YEARS

PPM

BT/Cu

SB/Cu

CHROMIUM

0

2

4

6

8

10

12

0-10 10--20 20-30 40-50 50-60 80-90 100-110

120-130

130-140

140-150

150-160

BAYOU STATIONS

PPM

Mean level of Cr is 6.6 at Stations 0-60 and 7.4 at Stations 80-160.

CHROMIUM CONCENTRATION IN BALDCYPRESS FROM BAYOU TREPAGNIER AND STINKING BAYOU

0

2

4

6

8

10

12

14

1905

1910

1915

1920

1925

1930

1935

1940

1945

1950

1955

1960

1965

1970

1975

1980

1985

1990

1995

TREE RING YEARS

PPM

BT/Cr

SB/Cr

MANGANESE

0

10

20

30

40

50

60

0-10 10--20 20-30 40-50 50-60 80-90 100-110 120-130 130-140 140-150 150-160

BAYOU STATIONS

PPM

Mean level of Mn is 20.2 at Stations 0-60 and 29.1 at Stations 80-160.

Manganese

0

10

20

30

40

50

60

1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000

Tree Ring Years

PPM

Bayou Trepagnier

Stinking Bayou

IRON

0

200

400

600

800

1000

1200

1400

16000-

10

10--2

0

20-3

0

40-5

0

50-6

0

80-9

0

100-

110

120-

130

130-

140

140-

150

150-

160

BAYOU STATIONS

ppm

Mean level of Fe is 674 at Stations 0-60 and 652 at Stations 80-160.

IRON CONCENTRATION IN BALDCYPRESS FROM BAYOU TREPAGNIER AND STINKING BAYOU

0

200

400

600

800

1000

1200

1400

1600

1800

200019

10

1915

1920

1925

1930

1935

1940

1945

1950

1955

1960

1965

1970

1975

1980

1985

1990

1995

TREE RING YEARS

PPM

SB/Fe

BT/Fe

Conclusions

• Metal mobility and availability are different in wetland soils.

• Sulfate in the brackish water is reduced to sulfide and reacts with metals to form precipitates.

• The sediments are highly polluted but precipitates are stable as long as reducing conditions are maintained.

• Fe and Mn are more soluble and available to plants in the reduced state. This may account for their higher concentration in the tree rings.

Conclusions

• Waterlogged soil, circumneutral to basic pH, and acid volatile sulfides from brackish lake water are the cause of relatively low levels of metals in tree rings in spite of heavily polluted soil.

• Recently the levels of all metals in Stinking Bayou and levels of Cr, Mg and Fe in Bayou Trepagnier, likely due to urbanization.