In-Situ Molecular-Level Elucidation of Organofluorine Binding Sites in a Whole Peat Soil

Abstract

The chemical nature of xenobiotic binding sites in soils is of vital importance to environmental biogeochemistry. Interactions between xenobiotics and the naturally occurring organic constituents of soils are strongly correlated to environmental persistence, bioaccessibility, and ecotoxicity. Nevertheless, because of the complex structural and chemical heterogeneity of soils, studies of these interactions are most commonly performed indirectly, using correlative methods, fractionation, or chemical modification. Here we identify the organic components of an unmodified peat soil where some organofluorine xenobiotic compounds interact using direct molecular-level methods. Using (19)F→(1)H cross-polarization magic angle spinning (CP-MAS) nuclear magnetic resonance (NMR) spectroscopy, the (19)F nuclei of organofluorine compounds are used to induce observable transverse magnetization in the (1)H nuclei of organic components of the soil with which they interact after sorption. The observed (19)F→(1)H CP-MAS spectra and dynamics are compared to those produced using model soil organic compounds, lignin and albumin. It is found that lignin-like components can account for the interactions observed in this soil for heptafluoronaphthol (HFNap) while protein structures can account for the interactions observed for perfluorooctanoic acid (PFOA). This study employs novel comprehensive multi-phase (CMP) NMR technology that permits the application of solution-, gel-, and solid-state NMR experiments on intact soil samples in their swollen state.

Comprehensive multiphase NMR: a promising technology to study plants in their native state

“…Based on the diffusion editing experiments ( H NMR alone were hampered because of spectral overlap. This limitation can be partially overcome by using 1D 13 C NMR. Carbon-13 has a greater chemical shift dispersion than protons (~200 ppm vs~10 ppm) that provides additional spectral dispersion.…”

“…Increased spectral dispersion enables overlapping resonances to be resolved and individual components to be assigned with increased confidence. From the 13 C NMR spectrum, several important metabolites, including adenine, phenylalanine, lipids, tyrosine, uridine, methanol, glycine-like compounds, and glutamine, were identified ( Fig. 3).…”

“…As expected, eli1 had more metabolites related to the lignin biosynthetic pathway, as indicated by monolignol aromatic signals or the hydroxyl phenyl units. [21][22][23][24] 1D solid-state 13 C NMR spectra of Arabidopsis thaliana seedlings So far in this study, only soluble metabolites and gel-like components have been investigated; to gain insights into the rigid structural components, solid-state NMR techniques are required. The 1D C through a dipolar network that arises in solids.…”

NMR in the environmental industry

“…[9] The use of lower magnetic fields, such as those provided by permanent rare earth magnets, while traditionally limited to relaxometry applications, has several potential advantages over the use of stronger magnetic fields for the analysis of environmental materials, including the ability to analyze larger samples in order to better account for sample heterogeneity, reduced influence of paramagnetic species in natural samples, and portability. [10] The use of permanent magnets for NMR analysis has traditionally been limited to applications of spin relaxometry, such as the well-logging example described in the preceding text.…”

Interactions between natural organic matter and organic pollutants as revealed by NMR spectroscopy

“…[128] In particular, the 19 F nuclei of organofluorine compounds were used to induce observable [127] Copyright 2014 by American Chemical Society). transverse magnetization to the 1 H nuclei in the peat molecular components, which were in direct interaction with the sorbed xenobiotics.…”