Solid-State ¹⁹F NMR Investigation of Hexafluorobenzene Sorption to Soil Organic Matter

Abstract

Solid-state 19F NMR observation of the sorptive uptake of hexafluorobenzene (HFB) by two peat samples gives direct spectroscopic evidence for the existence of dual-mode sorption to soil organic matter. The sorption process is shown to be rapid, with all applied HFB sorbed within a few hours. Extractable lipids compete for high energy sorption sites in the organic matter, and their removal increases the amount of rigidly sorbed, immobile species formed. Soil lipids enhance the sorption capacity of the solid-state dissolution domain of the organic matter. This dissolution domain is responsible for partitioning in the dual-mode phenomenon. Removal of the lipids decreases the partitioning capacity of the soil organic matter.

Applications of Fractals in the Study of Humic Materials

“…In this process, partitioning is a significant contribution to the overall sorption process at long equilibration times. Interestingly, this sequence of events is what Kohl et al [59] have observed when solid-state 19 F NMR is used to follow the interaction of hexafluorobenzene with natural organic matter sorbents.…”

Black carbon evaluation in natural organic matter samples using recoupled long-range dipolar dephasing solid-state 13C NMR

“…This observation may further suggest that there are different sorption domains in natural organic matter for GPP and IHSS leonardite. These domains may be dependent on the organization of natural organic matter components with different molecular weights and/or structural characteristics (Ding and Rice, 2011;Khalaf et al, 2003;Kohl et al, 2000).…”

Nuclear Magnetic Resonance Analysis of Natural Organic Matter

“…Cadmium NMR studies have been used to quantify 113 Cd binding (Chung et al, 1996 ;Larive et al, 1996 ;Otto et al, 2001b ), evaluate chemical exchange (Larive et al, 1996 ), identify the groups (mainly oxygen, but also nitrogen and sulfur at certain pH values) responsible for binding (Hertkorn et al, 2004 ), and identify specifi c (inner/outer sphere) complexes (Grassi and Daquino, 2005 ). Similarly, in the area of organic contaminant interactions, a wide array of studies have been performed (Thorn et al, 1996a(Thorn et al, ,b, 1997Bortiatynski et al, 1997 ;Hinedi et al, 1997 ;Jayasundera et al, 1997 ;Nanny et al, 1997 ;Achtnich et al, 1999 ;Dixon et al, 1999 ;Green et al, 1999 ;Knicker et al, 1999 ;Nanny, 1999 ;Xiong et al, 1999 ;Bruns -Nagel et al, 2000 ;Kohl et al, 2000 ;Emery et al, 2001 ;Smernik and Oades, 2001 ;Kacker et al, 2002 ;Thorn and Kennedy, 2002 ;Strynar et al, 2004 ;Smernik et al, 2006 ). Using NMR, it has been possible to determine the amount of organic contaminants bound (Simpson et al, 2004c ), evaluate binding type (covalent and noncovalent) (Nanny et al, 1997 ;Achtnich et al, 1999 ;Nanny and Maza, 2001 ), extract mechanistic information (Wais et al, 1996 ;Hinedi et al, 1997 ), and even focus on the structural components of NOM involved .…”

“…In the case of metal NMR studies, the observed nucleus is most commonly the metal itself -for example, 113 Cd studies (Dehorter et al, 1992 ;Larive et al, 1996 ;Li et al, 1998 ;Otto et al, 2001a,b ;Hertkorn et al, 2004 ;Grassi and Daquino, 2005 ). In the case of an organic species, many different contaminant nuclei have been studied, including: 1 H Simpson et al, 2004c ), 2 H (Nanny, 1999 ;Nanny and Maza, 2001 ), 13 C (Hatcher et al, 1993 ;Wais et al, 1996 ), 15 N ( Thorn et al, 1996aThorn et al, ,b, 1997Weber et al, 1996 ), and 19 F (Kohl et al, 2000 ;Khalaf et al, 2003 ;Strynar et al, 2004 ). Figure 15.15 shows an example where the chemical shift of the contaminant can change drastically when interacting with NOM in a whole soil.…”