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Statements

Subject Item
n2:RIV%2F60077344%3A_____%2F13%3A00394923%21RIV14-AV0-60077344
rdf:type
n5:Vysledek skos:Concept
dcterms:description
Humic substances play an important role in many environmental processes such as sequestration and transport of hydrophobic compounds. The supramolecular character of humic substances imparts high flexibility of the aggregates associated with their variable reactivity under different conditions. In this study, heat-induced transitions and character of the hydration shell of sodium salts of humic and fulvic acids originating from various sources were investigated using ultrasonic velocimetry in the temperature interval from 5 to 90 °C. Results clearly showed differences in stability and characteristics of the hydrated states at concentrations above and below 1 g L-1 with the exception of Pahokee peat fulvic acids. It has been concluded that predominantly the relaxation part of the adiabatic compressibility plays an important role below 1 g L-1 in contrast to both relaxation and intrinsic parts of the compressibility being important at higher concentrations. Dilution brought several temperature induced transitions which were investigated with respect to composition of all investigated humic substances. Correlation analysis revealed that the transition around 17 °C is associated with disruption of H-interactions whereas the transition around 42 °C depends on the aromaticity. Comparison of cooling and heating records revealed hysteresis in the structural relaxation resembling the behavior of physically stabilized hydrogels. Results indicated a difference in the conformation and therefore reactivity of dissolved humic substances in the dependence on temperature and thermal history. It has been hypothesized that this may play an important role in the transport and sequestration of hydrophobic pollutants by dissolved organic matter. Humic substances play an important role in many environmental processes such as sequestration and transport of hydrophobic compounds. The supramolecular character of humic substances imparts high flexibility of the aggregates associated with their variable reactivity under different conditions. In this study, heat-induced transitions and character of the hydration shell of sodium salts of humic and fulvic acids originating from various sources were investigated using ultrasonic velocimetry in the temperature interval from 5 to 90 °C. Results clearly showed differences in stability and characteristics of the hydrated states at concentrations above and below 1 g L-1 with the exception of Pahokee peat fulvic acids. It has been concluded that predominantly the relaxation part of the adiabatic compressibility plays an important role below 1 g L-1 in contrast to both relaxation and intrinsic parts of the compressibility being important at higher concentrations. Dilution brought several temperature induced transitions which were investigated with respect to composition of all investigated humic substances. Correlation analysis revealed that the transition around 17 °C is associated with disruption of H-interactions whereas the transition around 42 °C depends on the aromaticity. Comparison of cooling and heating records revealed hysteresis in the structural relaxation resembling the behavior of physically stabilized hydrogels. Results indicated a difference in the conformation and therefore reactivity of dissolved humic substances in the dependence on temperature and thermal history. It has been hypothesized that this may play an important role in the transport and sequestration of hydrophobic pollutants by dissolved organic matter.
dcterms:title
Origin of heat-induced structural changes in dissolved organic matter Origin of heat-induced structural changes in dissolved organic matter
skos:prefLabel
Origin of heat-induced structural changes in dissolved organic matter Origin of heat-induced structural changes in dissolved organic matter
skos:notation
RIV/60077344:_____/13:00394923!RIV14-AV0-60077344
n5:predkladatel
n6:ico%3A60077344
n3:aktivita
n13:I
n3:aktivity
I
n3:cisloPeriodika
2
n3:dodaniDat
n7:2014
n3:domaciTvurceVysledku
n12:9522999
n3:druhVysledku
n14:J
n3:duvernostUdaju
n16:S
n3:entitaPredkladatele
n17:predkladatel
n3:idSjednocenehoVysledku
94643
n3:idVysledku
RIV/60077344:_____/13:00394923
n3:jazykVysledku
n18:eng
n3:klicovaSlova
dissolved organic matter; humic substances; hydration; hysteresis
n3:klicoveSlovo
n4:hysteresis n4:hydration n4:humic%20substances n4:dissolved%20organic%20matter
n3:kodStatuVydavatele
GB - Spojené království Velké Británie a Severního Irska
n3:kontrolniKodProRIV
[085C7E548033]
n3:nazevZdroje
Chemosphere
n3:obor
n8:DF
n3:pocetDomacichTvurcuVysledku
1
n3:pocetTvurcuVysledku
3
n3:rokUplatneniVysledku
n7:2013
n3:svazekPeriodika
90
n3:tvurceVysledku
Novák, František Kučerík, J. Drastík, M.
n3:wos
000312618300087
s:issn
0045-6535
s:numberOfPages
7
n10:doi
10.1016/j.chemosphere.2012.09.076