sample treatment causes changes:
Sr/Ca: NaOH treatment
=> significant decrease :
=> no clear pattern
=> tendency to increase Mg/Ca, Ba/Ca, Mn/Ca
most efficient removers:
=>NaOCl
(treatment# 5,9,12)
=>NaOH
(treatment# 4,8,11,12)
TE concentrations
Trace elements in biogenic carbonates – do not mess with the organic matrix!
J. Krause-Nehring , 1
1 2
jacqueline.krause-nehring@awi.de Alfred Wegener Institute for Polar and Marine Research, Germany University of Bremen, Germany
2 1 1 1
A. Klügel , G. Nehrke , M. Kriews , and T. Brey
0 no treatment 1 w ashing only 2 Acetone
3 H2O2 4 NaOH 5 NaOCl 6 Mucasol
7 Acetone+H2O2+Acetone 8 Acetone+NaOH+Acetone 9 Acetone+NaOCl+Acetone 10 Acetone+Mucasol+Acetone
11 Acetone+H2O2+NaOH+Acetone 12 Acetone+H2O2+NaOH+NaOCl
+Mucasol+Acetone
Rationale
Numerous attempts to correlate trace element (TE) concentrations in biogenic carbonates with environmental parameters led to contradictory results. The organic matrix may be one reason for these inconsistencies.
Proxy analyses imply that physical processes control trace element incorporation in biogenic carbonates.
Thus, the biogeochemistry of the carbonate and environmental parameters during shell formation are directly connected. Incorporation of trace elements into the organic matrix, however, is also controlled by physiological processes – that is the problem!
We evaluate the effect of the organic matrix on trace element concentrations in biogenic carbonates. We use bivalve shell powder (Arctica islandica) to examine the effect of 12 treatments on:
?TE concentrations (Mg/Ca, Sr/Ca, Ba/Ca, Mn/Ca) AND
?Organic matter content ( N content)
Results
What´s next Methods
A. islandica shell
» one valve
shell powder
» grain size ~30µm
13 subsamples
» 12 treatments + control
TE and
» Mg/Ca, Sr/Ca, Ba/Ca, Mn/Ca N measurements
cleaning + grinding
division
1. Can we reproduce our analyses with intact shells => same pattern?
A. islandica shell cross-section of the shell umbo with LA-ICP-MS tracks
Organic matter content
2. Combine spatial TE map (LA-ICP-MS, microprobe) with spatial mapping of organic matter (RAMAN)
B23E-0420
Mg/Ca Sr/Ca Ba/Ca Mn/Ca
decrease no effect
increase N content ( µg / mg )
1 2 3 4 5 6 7 8 9 10 11 12
Mg/Ca Sr/Ca Ba/Ca Mn/Ca
decrease no effect
increase N content ( µg / mg )
1 2 3 4 5 6 7 8 9 10 11 12
0.00 0.10 0.20 0.30 0.40 0.50 0.60 0.70
Sr/Ca sample profile
( untreated sample) 1 - 12 = treatment # ( see “Methods”)
Target TE determines sample pre-treatment:
?
=> remove organic matrix prior to measurements
?
