Details
| Original language | English |
|---|---|
| Pages (from-to) | 87-95 |
| Number of pages | 9 |
| Journal | GEODERMA |
| Volume | 282 |
| Publication status | Published - 15 Nov 2016 |
| Externally published | Yes |
Abstract
Mollusk shells are commonly present in a broad array of geological and archaeological contexts. The shell carbonate can serve for numerical age determination (Δ14C) and as a paleoenvironmental indicator (δ18O, δ13C). Shell carbonate recrystallization in soils, however, may re-equilibrate the carbon (C) isotopic signature with soil CO2. The equilibration dynamics remain poorly understood because of the absence of suitable experimental approaches. Here we used the artificial 14C-labeling technique to study the process of shell carbonate recrystallization as a function of time. Organic-free and organic-containing shell particles of Protothaca staminea were mixed with loess or a carbonate-free loamy soil. The mixtures were placed in air-tight bottles, where the bottle air containing 14CO2 (pCO2 = 2%). The 14C activity of shells was measured over time and related to the recrystallization of shell carbonate. Recrystallization of shell carbonate already began after one day. The recrystallization rates were 10− 3% day− 1 in organic-containing shell embedded in soil and 1.6 · 10− 2% day− 1 in organic-free shells in loess. Removal of organic compounds increased shell porosity, and so, increased the contact surface for exchange with soil solution. Organic-free shells recrystallized much faster in loess (0.56% in 56 days) than in other treatments. Recrystallization was 2 to 7 times higher in loess (in the presence and absence of organic compounds, respectively) than in carbonate-free soil. Loess carbonate itself can recrystallize and accumulate on shells, leading to overestimation of shell carbonate recrystallization. A model for shell carbonate recrystallization as a function of time was developed. The model considers the presence or absence of organic compounds in shell structure and geogenic carbonates in the embedding matrix. The model enabled all results to be fitted with R2 = 0.98. The modelled time necessary for nearly full recrystallization (95% of shell carbonate) was 88 years for organic-free shells in loess and up to 770 years for organic-containing shells in carbonate-free soil. After this period, the original isotopic signature will vanish completely and will be replaced by a new δ13C and Δ14C signature in the shell structure. Thus, shell carbonate recrystallization may proceed relatively rapidly in terms of geologic time. This is necessary to consider in the interpretation of dating results and paleoenvironmental reconstructions.
Keywords
- C labeling, Biogenic carbonates, Geogenic carbonates, Porosity, Recrystallization, Shell
ASJC Scopus subject areas
- Agricultural and Biological Sciences(all)
- Soil Science
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In: GEODERMA, Vol. 282, 15.11.2016, p. 87-95.
Research output: Contribution to journal › Article › Research › peer review
}
TY - JOUR
T1 - Recrystallization of shell carbonate in soil
T2 - 14C labeling, modeling and relevance for dating and paleo-reconstructions
AU - Zamanian, Kazem
AU - Pustovoytov, Konstantin
AU - Kuzyakov, Yakov
N1 - Funding information: We acknowledge Heidelberg Cement AG for sampling permission in their queries specially Dr. Manfred Löscher for discussion in the field. We would like to thank Anita Kriegel and Shibin Liu for their help during sampling and analyses. Special thanks to Ingrid Ostermeyer and Martina Gebauer for measuring soil properties and the elemental composition of shells. We gratefully acknowledge Mohsen Zarebanadkouki for his comments on the manuscript and Kyle Mason-Jones for English editing of the text. The study was supported by German Research Foundation (DFG) ( KU 1184/34-1 ).
PY - 2016/11/15
Y1 - 2016/11/15
N2 - Mollusk shells are commonly present in a broad array of geological and archaeological contexts. The shell carbonate can serve for numerical age determination (Δ14C) and as a paleoenvironmental indicator (δ18O, δ13C). Shell carbonate recrystallization in soils, however, may re-equilibrate the carbon (C) isotopic signature with soil CO2. The equilibration dynamics remain poorly understood because of the absence of suitable experimental approaches. Here we used the artificial 14C-labeling technique to study the process of shell carbonate recrystallization as a function of time. Organic-free and organic-containing shell particles of Protothaca staminea were mixed with loess or a carbonate-free loamy soil. The mixtures were placed in air-tight bottles, where the bottle air containing 14CO2 (pCO2 = 2%). The 14C activity of shells was measured over time and related to the recrystallization of shell carbonate. Recrystallization of shell carbonate already began after one day. The recrystallization rates were 10− 3% day− 1 in organic-containing shell embedded in soil and 1.6 · 10− 2% day− 1 in organic-free shells in loess. Removal of organic compounds increased shell porosity, and so, increased the contact surface for exchange with soil solution. Organic-free shells recrystallized much faster in loess (0.56% in 56 days) than in other treatments. Recrystallization was 2 to 7 times higher in loess (in the presence and absence of organic compounds, respectively) than in carbonate-free soil. Loess carbonate itself can recrystallize and accumulate on shells, leading to overestimation of shell carbonate recrystallization. A model for shell carbonate recrystallization as a function of time was developed. The model considers the presence or absence of organic compounds in shell structure and geogenic carbonates in the embedding matrix. The model enabled all results to be fitted with R2 = 0.98. The modelled time necessary for nearly full recrystallization (95% of shell carbonate) was 88 years for organic-free shells in loess and up to 770 years for organic-containing shells in carbonate-free soil. After this period, the original isotopic signature will vanish completely and will be replaced by a new δ13C and Δ14C signature in the shell structure. Thus, shell carbonate recrystallization may proceed relatively rapidly in terms of geologic time. This is necessary to consider in the interpretation of dating results and paleoenvironmental reconstructions.
AB - Mollusk shells are commonly present in a broad array of geological and archaeological contexts. The shell carbonate can serve for numerical age determination (Δ14C) and as a paleoenvironmental indicator (δ18O, δ13C). Shell carbonate recrystallization in soils, however, may re-equilibrate the carbon (C) isotopic signature with soil CO2. The equilibration dynamics remain poorly understood because of the absence of suitable experimental approaches. Here we used the artificial 14C-labeling technique to study the process of shell carbonate recrystallization as a function of time. Organic-free and organic-containing shell particles of Protothaca staminea were mixed with loess or a carbonate-free loamy soil. The mixtures were placed in air-tight bottles, where the bottle air containing 14CO2 (pCO2 = 2%). The 14C activity of shells was measured over time and related to the recrystallization of shell carbonate. Recrystallization of shell carbonate already began after one day. The recrystallization rates were 10− 3% day− 1 in organic-containing shell embedded in soil and 1.6 · 10− 2% day− 1 in organic-free shells in loess. Removal of organic compounds increased shell porosity, and so, increased the contact surface for exchange with soil solution. Organic-free shells recrystallized much faster in loess (0.56% in 56 days) than in other treatments. Recrystallization was 2 to 7 times higher in loess (in the presence and absence of organic compounds, respectively) than in carbonate-free soil. Loess carbonate itself can recrystallize and accumulate on shells, leading to overestimation of shell carbonate recrystallization. A model for shell carbonate recrystallization as a function of time was developed. The model considers the presence or absence of organic compounds in shell structure and geogenic carbonates in the embedding matrix. The model enabled all results to be fitted with R2 = 0.98. The modelled time necessary for nearly full recrystallization (95% of shell carbonate) was 88 years for organic-free shells in loess and up to 770 years for organic-containing shells in carbonate-free soil. After this period, the original isotopic signature will vanish completely and will be replaced by a new δ13C and Δ14C signature in the shell structure. Thus, shell carbonate recrystallization may proceed relatively rapidly in terms of geologic time. This is necessary to consider in the interpretation of dating results and paleoenvironmental reconstructions.
KW - C labeling
KW - Biogenic carbonates
KW - Geogenic carbonates
KW - Porosity
KW - Recrystallization
KW - Shell
UR - http://www.scopus.com/inward/record.url?scp=84978531604&partnerID=8YFLogxK
U2 - 10.1016/j.geoderma.2016.07.013
DO - 10.1016/j.geoderma.2016.07.013
M3 - Article
AN - SCOPUS:84978531604
VL - 282
SP - 87
EP - 95
JO - GEODERMA
JF - GEODERMA
SN - 0016-7061
ER -