HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Abstract Full Text Free Full Text (PDF) Free Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Simpson, M. J. Search for Related Content PubMed Articles by Simpson, M. J. Agricola Articles by Simpson, M. J. Related Collections Humic Substances Organic Compounds Soil Pollution Soil Chemistry

Nuclear Magnetic Resonance Based Investigations of Contaminant Interactions with Soil Organic Matter

Dep. of Physical and Environmental Sciences, Univ. of Toronto, Scarborough College, 1265 Military Trail, Toronto, ON M1C 1A4, Canada

View larger version (31K): [in a new window]   Fig. 1. A proposed multitiered approach to studying organic contaminant interactions with soils. Most investigations occur at the landscape or macroscopic-level; however, combining all three approaches will result in a fundamental understanding of contaminant fate in terrestrial environments.

View larger version (28K): [in a new window]   Fig. 2. An illustration of (A) macroscopic-level and (B) molecular-level data. Macroscopic data has yielded a multitude of indirect hypotheses which are now being refined with the application of direct, molecular-level observations. Macroscopic methods commonly employ batch equilibration experiments that produce sorption isotherms (note: not all sorption isotherms are nonlinear; linearity varies with sorbate and sorbent properties and the type of mechanisms that are dominating the attenuation process). Molecular-level studies enable sorption mechanisms, such as those between trifluralin and SOM (adapted from Simpson et al., 2001). Two-dimensional molecular-level data, such as correlation spectroscopy NMR of a soil humic acid, displayed from Simpson et al. (2004), can provide detailed structural information about humic material and can be used to decipher specific SOM interactions with contaminants. Reprinted with permission from Simpson et al. (2004). Copyright (2004) Environmental Toxicology and Chemistry, Alliance Communications Group.

View larger version (28K): [in a new window]   Fig. 3. Solid-state 13C CP/MAS NMR spectra of chemically modified humic acids from Simpson et al. (2003). The selective removal of SOM components suggests that structures such as polymethylene carbon may be blocked by other humic structures. Only through chemical modification do they become more available in contaminant interactions. Reprinted with permission from Simpson et al. (2003).

View larger version (18K): [in a new window]   Fig. 4. (A) Data from (Simpson et al., 2004) displaying the decline in 1H T1 values of 1-naphthol with increasing concentration of soil humic acid (HA). The measurements indicate that all protons are equally interacting and hence, a specific interaction between individual nuclei (1H in this example) and the HA is not observed, suggesting a strong interaction with all protons in the molecule with HA. (B) The aromatic region from the 1H spectrum does not reveal a change in chemical shift, suggesting that this is a strictly noncovalent interaction. The increased line broadening with the addition of 50 mg C L–1 of HA is indicative of a strong, noncovalent association. Reprinted with permission from Simpson et al. (2004). Copyright (2004) Environmental Toxicology and Chemistry, Alliance Communications Group.