TY - JOUR

T1 - Effect of multivalent cations, temperature, and aging on SOM thermal properties

AU - Diehl, Dörte

AU - Schwarz, Jette

AU - Goebel, Marc O.

AU - Woche, Susanne K.

AU - Schneckenburger, Tatjana

AU - Krüger, Jaane

AU - Shchegolikhina, Anastasia

AU - Marschner, Bernd

AU - Lang, Friederike

AU - Thiele-Bruhn, Sören

AU - Bachmann, Jörg

AU - Schaumann, Gabriele E.

N1 - Funding Information: Acknowledgements The presented study was supported by the German Research Foundation (Deutsche Forschungsgemeinschaft) within the priority program SPP 1315 ‘‘Biogeochemical Interfaces in Soil’’ projects SCHA849/8, BA1359/9, KA1139/15, TH678/10, and LA1398/7-2 and the CROSSLINK project (SCHA849/6-1). Publisher Copyright: © 2014 Akadémiai Kiadó, Budapest, Hungary. Copyright: Copyright 2015 Elsevier B.V., All rights reserved.

PY - 2014/7/30

Y1 - 2014/7/30

N2 - Multivalent cations are suggested to influence the supramolecular structure of soil organic matter (SOM) via inter- and intra-molecular interactions with SOM functional groups. In this study, we tested the combined effect of cations, temperature treatment, and isothermal aging on SOM matrix properties. Samples from a peat and a mineral soil were either enriched with Na, Ca, and Al or desalinated in batch experiments. After treatment at 25, 40, 60, and 105 °C and after different periods of aging at 19 °C and 31 % relative humidity, we investigated the physicochemical matrix stability and the thermal stability against combustion. We hypothesized that multivalent cations stabilize the SOM matrix, that these structures disrupt at elevated temperatures, and that aging leads to an increase in matrix stability. The results show that cation-specific effects on matrix rigidity started to evolve in the peat only after 8 weeks of aging and were significantly lower than the temperature effects. Temperature treatment above 40 °C caused a non (or not immediately) reversible loss of water molecule bridges (WaMB) and above 60 °C a partly reversible melting process probably of semi-crystalline poly(methylene). Thermal stability increased with increasing cation valence and degree of protonation and was much less affected by temperature. Generally, Na-treated and control samples revealed lower thermal stability and lower increase in matrix rigidity with aging than those treated with Ca, Al, and H. We conclude that drying at elevated temperatures (>40 °C) may irreversibly change SOM structure via disruption of labile cross-links and melting of semi-crystalline domains.

AB - Multivalent cations are suggested to influence the supramolecular structure of soil organic matter (SOM) via inter- and intra-molecular interactions with SOM functional groups. In this study, we tested the combined effect of cations, temperature treatment, and isothermal aging on SOM matrix properties. Samples from a peat and a mineral soil were either enriched with Na, Ca, and Al or desalinated in batch experiments. After treatment at 25, 40, 60, and 105 °C and after different periods of aging at 19 °C and 31 % relative humidity, we investigated the physicochemical matrix stability and the thermal stability against combustion. We hypothesized that multivalent cations stabilize the SOM matrix, that these structures disrupt at elevated temperatures, and that aging leads to an increase in matrix stability. The results show that cation-specific effects on matrix rigidity started to evolve in the peat only after 8 weeks of aging and were significantly lower than the temperature effects. Temperature treatment above 40 °C caused a non (or not immediately) reversible loss of water molecule bridges (WaMB) and above 60 °C a partly reversible melting process probably of semi-crystalline poly(methylene). Thermal stability increased with increasing cation valence and degree of protonation and was much less affected by temperature. Generally, Na-treated and control samples revealed lower thermal stability and lower increase in matrix rigidity with aging than those treated with Ca, Al, and H. We conclude that drying at elevated temperatures (>40 °C) may irreversibly change SOM structure via disruption of labile cross-links and melting of semi-crystalline domains.

KW - Cation

KW - Combustion enthalpy

KW - Differential scanning calorimetry (DSC)

KW - Soil organic matter (SOM)

KW - Step transition

UR - http://www.scopus.com/inward/record.url?scp=84911992229&partnerID=8YFLogxK

U2 - 10.1007/s10973-014-3989-7

DO - 10.1007/s10973-014-3989-7

M3 - Article

AN - SCOPUS:84911992229

VL - 118

SP - 1203

EP - 1213

JO - Journal of Thermal Analysis and Calorimetry

JF - Journal of Thermal Analysis and Calorimetry

SN - 1388-6150

IS - 2

ER -