TY  - JOUR
A1  - Burek, Katja
A1  - Krause, Felix
A1  - Schwotzer, Matthias
A1  - Nefedov, Alexei
A1  - Süssmuth, Julia
A1  - Haubitz, Toni
A1  - Kumke, Michael Uwe
A1  - Thissen, Peter
T1  - Hydrophobic Properties of Calcium-Silicate Hydrates Doped with Rare-Earth Elements
JF  - ACS sustainable chemistry & engineering
N2  - In this study, the apparent relationship between the transport process and the surface chemistry of the Calcium-Silicate Hydrate (CSH) phases was investigated. For this purpose, a method was developed to synthesize ultrathin CSH phases to be used as a model substrate with the specific modification of their structure by introducing europium (Eu(III)). The structural and chemical changes during this Eu(III)-doping were observed by means of infrared spectroscopy (IR), X-ray photoelectron spectroscopy (XPS), and time-resolved laser fluorescence spectroscopy (TRLFS). These alterations of the CSH phases led to significant changes in the surface chemistry and consequently to considerable variations in the interaction with water, as evidenced by measurements of the contact angles on the modified model substrates. Our results provide the basis for a more profound molecular understanding of reactive transport processes in cement-based systems. Furthermore, these results broaden the perspective of improving the stability of cement-based materials, which are subjected to the impact of aggressive aqueous environments through targeted modifications of the CSH phases.
KW  - Rare-earth elements
KW  - Europium
KW  - Luminescence
KW  - Metal-proton exchange reaction
KW  - Contact angle
KW  - Infrared spectroscopy
KW  - X-ray photoelectron spectroscopy
Y1  - 2018
U6  - https://doi.org/10.1021/acssuschemeng.8b03244
SN  - 2168-0485
VL  - 6
IS  - 11
SP  - 14669
EP  - 14678
PB  - American Chemical Society
CY  - Washington
ER  - 
TY  - JOUR
A1  - Kaiser, Michael
A1  - Zederer, Dan P.
A1  - Ellerbrock, Ruth H.
A1  - Sommer, Michael
A1  - Ludwig, Bernard
T1  - Effects of mineral characteristics on content, composition, and stability of organic matter fractions separated from seven forest topsoils of different pedogenesis
JF  - Geoderma : an international journal of soil science
N2  - Mineral topsoils possess large organic carbon (OC) contents but there is only limited knowledge on the mechanisms controlling the preservation of organic matter (OM) against microbial decay. Samples were taken from the uppermost mineral topsoil horizon (0 to 5 cm) of seven sites under mature deciduous forest showing OC contents between 69 and 164 g kg(-1) and a wide range in mineral characteristics. At first, organic particles and the water-extractable OM were removed from the soil samples. Thereafter, Na-pyrophosphate extractable organic matter (OM(PY)), assumed to be indicative for OM bound via cation mediated interactions, and the OM remaining in the extraction residue (OM(ER)), supposed to be indicative for OM occluded in mechanically highly stable micro-aggregates, were sequentially separated and quantified. The composition of OM(PY) and OM(ER) was analyzed by FTIR and their stability by C-14 measurements. The OC remaining in the extraction residues accounted for 38 to 59% of the bulk soil OC (SOC) suggesting a much larger relevance of OM(ER) for the OM dynamic in the analyzed soils as compared with OM(PY) that accounted for 1.6 to 7.5% of the SOC. The FUR analyses revealed a lower relative proportion of C=O groups in OM(ER) compared to OM(PY) indicating differences in the degree of microbial processing between these fractions. Correlation analyses suggest an increase in the stability of OM(PY) with the soil pH and contents of Na-pyrophosphate soluble Fe, Al, and Mg and an increase in the stability of OM(ER) with the soil pH and the contents of clay and oxalate-soluble Fe and Al. Despite the detected influence of soil mineral characteristics on the turnover of OM(PY) and OM(ER), the Delta C-14 signatures indicated mean residence times less than 100 years. The presence of less stabilized OM in these fractions can be derived from methodological uncertainties and/or the fast cycling compartment of mineral-associated OM. (C) 2015 Elsevier B.V. All rights reserved.
KW  - Forest mineral topsoil
KW  - Organic matter stabilization
KW  - Na-pyrophosphate soluble organic matter
KW  - Micro-aggregates
KW  - Infrared spectroscopy
KW  - C-14 analyses
Y1  - 2016
U6  - https://doi.org/10.1016/j.geoderma.2015.08.029
SN  - 0016-7061
SN  - 1872-6259
VL  - 263
SP  - 1
EP  - 7
PB  - Elsevier
CY  - Amsterdam
ER  -