TY  - JOUR
A1  - Puppe, Daniel
A1  - Leue, Martin
A1  - Sommer, Michael
A1  - Schaller, Jörg
A1  - Kaczorek, Danuta
T1  - Auto-fluorescence in phytoliths
BT  - a mechanistic understanding derived from microscopic and spectroscopic analyses
JF  - Frontiers in Environmental Science
N2  - The detection of auto-fluorescence in phytogenic, hydrated amorphous silica depositions (phytoliths) has been found to be a promising approach to verify if phytoliths were burnt or not, especially in archaeological contexts. However, it is unknown so far at what temperature and how auto-fluorescence is induced in phytoliths. We used fluorescence microscopy, scanning electron microscope-energy dispersive X-ray spectroscopy (SEM-EDX), and Fourier transform infrared spectroscopy to analyze auto-fluorescence in modern phytoliths extracted from plant samples or in intact leaves of winter wheat. Leaves and extracted phytoliths were heated at different temperatures up to 600 degrees C. The aims of our experiments were i) to find out what temperature is needed to induce auto-fluorescence in phytoliths, ii) to detect temperature-dependent changes in the molecular structure of phytoliths related to auto-fluorescence, and iii) to derive a mechanistic understanding of auto-fluorescence in phytoliths. We found organic compounds associated with phytoliths to cause auto-fluorescence in phytoliths treated at temperatures below approx. 400 degrees C. In phytoliths treated at higher temperatures, i.e., 450 and 600 degrees C, phytolith auto-fluorescence was mainly caused by molecular changes of phytolith silica. Based on our results we propose that auto-fluorescence in phytoliths is caused by clusterization-triggered emissions, which are caused by overlapping electron clouds forming non-conventional chromophores. In phytoliths heated at temperatures above about 400 degrees C dihydroxylation and the formation of siloxanes result in oxygen clusters that serve as non-conventional chromophores in fluorescence events. Furthermore, SEM-EDX analyses revealed that extractable phytoliths were dominated by lumen phytoliths (62%) compared to cell wall phytoliths (38%). Our findings might be not only relevant in archaeological phytolith-based examinations, but also for studies on the temperature-dependent release of silicon from phytoliths and the potential of long-term carbon sequestration in phytoliths.
KW  - fluorescence microscopy
KW  - FTIR spectroscopy
KW  - SEM-EDX
KW  - burnt phytoliths;
KW  - carbon sequestration
Y1  - 2022
U6  - https://doi.org/10.3389/fenvs.2022.915947
SN  - 2296-665X
VL  - 10
PB  - Frontiers Media
CY  - Lausanne
ER  - 
TY  - GEN
A1  - Hodgkins, Suzanne B.
A1  - Richardson, Curtis J.
A1  - Dommain, René
A1  - Wang, Hongjun
A1  - Glaser, Paul H.
A1  - Verbeke, Brittany
A1  - Winkler, B. Rose
A1  - Cobb, Alexander R.
A1  - Rich, Virginia I.
A1  - Missilmani, Malak
A1  - Flanagan, Neal
A1  - Ho, Mengchi
A1  - Hoyt, Alison M.
A1  - Harvey, Charles F.
A1  - Vining, S. Rose
A1  - Hough, Moira A.
A1  - Moore, Tim R.
A1  - Richard, Pierre J. H.
A1  - De La Cruz, Florentino B.
A1  - Toufaily, Joumana
A1  - Hamdan, Rasha
A1  - Cooper, William T.
A1  - Chanton, Jeffrey P.
T1  - Tropical peatland carbon storage linked to global latitudinal trends in peat recalcitrance
T2  - Postprints der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe
N2  - Peatlands represent large terrestrial carbon banks. Given that most peat accumulates in boreal regions, where low temperatures and water saturation preserve organic matter, the existence of peat in (sub)tropical regions remains enigmatic. Here we examined peat and plant chemistry across a latitudinal transect from the Arctic to the tropics. Near-surface low-latitude peat has lower carbohydrate and greater aromatic content than near-surface high-latitude peat, creating a reduced oxidation state and resulting recalcitrance. This recalcitrance allows peat to persist in the (sub)tropics despite warm temperatures. Because we observed similar declines in carbohydrate content with depth in high-latitude peat, our data explain recent field-scale deep peat warming experiments in which catotelm (deeper) peat remained stable despite temperature increases up to 9 degrees C. We suggest that high-latitude deep peat reservoirs may be stabilized in the face of climate change by their ultimately lower carbohydrate and higher aromatic composition, similar to tropical peats.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 1125 
KW  - dissolved organic matter
KW  - greenhouse gas fluxes
KW  - permafrost thaw
KW  - Northern Minnesota
KW  - FTIR spectroscopy
KW  - lignin content
KW  - brown rot
KW  - decomposition
KW  - chemistry
KW  - dynamics
Y1  - 2021
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-459658
SN  - 1866-8372
IS  - 1125
ER  -