Improving Our Understanding of Contaminated

Environments Using Nuclear Magnetic

Resonance

James Longstaffe

Assistant Professor of Environmental Chemistry

School of Environmental Sciences

Ontario Agricultural College

University of Guelph

Canada

1) NMR as an analytical tool to understand what is present in

the environment?

2) NMR as a physical property tool to understand behavior?

Improved Understanding Environmental Risk & Behavior

The Road Towards Practical Applications

of NMR in the Environmental Sciences

Improved Remediation & Environmental Protection

1) NMR as an analytical tool to

characterize complex

contaminated environments

1.69% of the water on Earth is groundwater

In the US, groundwater supplies:39% of the public water supply37% of irrigation water supply54% of livestock water supply

Source: Liu, Emma. On notice for a drinking water crisis in Canada, 2015.

1H NMR of Contaminated Groundwater

Non-Aqueous Phase Liquids

• NAPLs are formed from free-flowing liquid contaminants (usually solvents).• Complex NAPL mixtures present at many legacy sites are difficult to characterize

using traditional, serparation-based methods that require significant dilution ofthe sample prior to analysis.

• At may sites, much of the composition of NAPL is uncharacterized.

Non-Aqueous Phase Liquids (NAPL)

Site A

1H NMR spectrum of a complex

NAPL

19F NMR of a Complex NAPL

1H DOSY of a Complex NAPL

2) NMR as a physical tool to

understand contaminant

attenuation in the environment

The mechanisms of contaminant

attenuation in the environment are poorly

understood at the molecular-level

?

Simple Partitioning (foc)

Binding to soils &

sediments

influences:

•Sequestration

•Bioavailability &

Bioaccesibliity

•Apparent Toxicity

•Mobility

Goal: Direct observation

of intermolecular interactions

in soils & sediments

Towards a Molecular-Level

Understanding of Contaminant

Attenuation in the Environment

Using NMR to Probe Intermolecular

Interactions in Soils

Fluorine-19 nuclei

Hydrogen-1 nuclei

Magnetic Dipole

Interaction

Soil Organic Matter

Identifying Binding Sites in Soil Organic Matter using 1H{19F} STD NMR

Protein

(Albumin)

Lignin

-111 9 7 5 3 1

Humic Acid

Protein &

Lignin

-111 9 7 5 3 1

Longstaffe, J. G. et al. Environ. Sci. Technol. 2010, 44 (14), 5476-5418.

Time Domain NMR of Metals in Soil

-2.5

-1.875

-1.25

-0.625

0.

0. 125. 250. 375. 500.

ln (

I/Io

)

Delay (s)

Clay Soil

(Mostly Bound)

R2 = 0.9486

Clay Soil

(Partially Bound)

R2 = 0.9027

Sand

(Mostly Free)

R2 = 0.9898

Solution (Free)

R2 = 0.9864

113Cadmium NMRT2 Measurements (CPMG)

Thanks, & Acknowledgments