TY - JOUR

T1 - Effect of multivalent cations, temperature and aging on soil organic matter interfacial properties

AU - Diehl, Dörte

AU - Schneckenburger, Tatjana

AU - Krüger, Jaane

AU - Göbel, Marc Oliver

AU - Woche, Susanne K.

AU - Schwarz, Jette

AU - Shchegolikhina, Anastasia

AU - Lang, Friederike

AU - Marschner, Bernd

AU - Thiele-Bruhn, Sören

AU - Bachmann, Jörg

AU - Schaumann, Gabriele E.

N1 - Publisher Copyright: © 2014 CSIRO. Copyright: Copyright 2015 Elsevier B.V., All rights reserved.

PY - 2014

Y1 - 2014

N2 - Environmental context The supramolecular structure and resulting physicochemical properties of soil organic matter (SOM) significantly control storage and buffer functions of soils, e.g. for nutrients, organic molecules and water. Multivalent cations, able to form complexes, are suggested to form inter- and intramolecular cross-links in SOM. At present, specific effects of the valence and type of cation on SOM properties are incompletely understood. We investigated changes in SOM interfacial properties, its ability to release mobile colloids in aqueous solutions and its sorption affinity towards organic chemicals in dependence on cation-SOM interactions, temperature and aging time. Abstract The present study aims to improve our understanding on the effect of multivalent cations, temperature treatment and isothermal aging time on interfacial soil organic matter (SOM) properties as major factors that modify its supramolecular structures. A sandy topsoil (LW) and a peat soil (SP) were enriched with Na, Ca or Al, or desalinated in a batch experiment, treated at 25, 40, 60 and 105°C and aged at constant temperature and humidity (20°C, 31% relative humidity). After aging for different periods, contact angles (CAs), sorption properties towards xenobiotics and properties of water dispersible colloids were determined. With increasing valence of the dominant cations fewer and larger colloids were observed, probably attributable to cation cross-links or enhanced aggregation caused by reduced surface charge. Al-enrichment of LW resulted in more abundant or more accessible sorption sites for hydrophobic xenobiotics. But in contrast to expectations, hydrophilic sorption as well as wettability was not significantly affected by the type of adsorbed cation. Increasing the temperature had a major effect on surface properties resulting in rising surface hydrophobisation with increasing solid-water CAs, decreasing surface O/C ratio and decreasing sorption of hydrophilic substances; whereas systematic temperature effects on water dispersible colloids and on hydrophobic sorption were not detected. Aging was found to increase the initial CA of the 25°C treatment and to increase the sorption of phenanthrene to LW for all treatment temperatures. We conclude that aging of SOM is a process that changes surface properties and approaches a new equilibrium state after a disturbance. The aging process may be significantly accelerated for samples treated at elevated temperatures.

AB - Environmental context The supramolecular structure and resulting physicochemical properties of soil organic matter (SOM) significantly control storage and buffer functions of soils, e.g. for nutrients, organic molecules and water. Multivalent cations, able to form complexes, are suggested to form inter- and intramolecular cross-links in SOM. At present, specific effects of the valence and type of cation on SOM properties are incompletely understood. We investigated changes in SOM interfacial properties, its ability to release mobile colloids in aqueous solutions and its sorption affinity towards organic chemicals in dependence on cation-SOM interactions, temperature and aging time. Abstract The present study aims to improve our understanding on the effect of multivalent cations, temperature treatment and isothermal aging time on interfacial soil organic matter (SOM) properties as major factors that modify its supramolecular structures. A sandy topsoil (LW) and a peat soil (SP) were enriched with Na, Ca or Al, or desalinated in a batch experiment, treated at 25, 40, 60 and 105°C and aged at constant temperature and humidity (20°C, 31% relative humidity). After aging for different periods, contact angles (CAs), sorption properties towards xenobiotics and properties of water dispersible colloids were determined. With increasing valence of the dominant cations fewer and larger colloids were observed, probably attributable to cation cross-links or enhanced aggregation caused by reduced surface charge. Al-enrichment of LW resulted in more abundant or more accessible sorption sites for hydrophobic xenobiotics. But in contrast to expectations, hydrophilic sorption as well as wettability was not significantly affected by the type of adsorbed cation. Increasing the temperature had a major effect on surface properties resulting in rising surface hydrophobisation with increasing solid-water CAs, decreasing surface O/C ratio and decreasing sorption of hydrophilic substances; whereas systematic temperature effects on water dispersible colloids and on hydrophobic sorption were not detected. Aging was found to increase the initial CA of the 25°C treatment and to increase the sorption of phenanthrene to LW for all treatment temperatures. We conclude that aging of SOM is a process that changes surface properties and approaches a new equilibrium state after a disturbance. The aging process may be significantly accelerated for samples treated at elevated temperatures.

KW - colloids

KW - contact angle

KW - sorption

KW - X-ray photoelectron spectroscopy.

UR - http://www.scopus.com/inward/record.url?scp=84918509941&partnerID=8YFLogxK

U2 - 10.1071/en14008

DO - 10.1071/en14008

M3 - Article

AN - SCOPUS:84918509941

VL - 11

SP - 709

EP - 718

JO - Environmental chemistry

JF - Environmental chemistry

SN - 1448-2517

IS - 6

ER -