NMR in Environmental Science
Little brown bats, western honey bees, and sunflower starfish are three very different species but they share one frightening predicament: their populations are under attack by contagions whose virulence is not fully understood. Each malady – White Nose Syndrome, Colony Collapse Disorder, and Sea Star Wasting Disease – has caused rapid population declines, but the full story behind the outbreaks is still unknown. They seem to arise from a deadly synergy: a combination of known pathogens, environmental degradation, and climate change.
The need to understand such synergies typifies the complex problems scientists face in the 21st century as climate change impacts and other environmental stressors increase.
NMR – A Flexible Tool for Investigating Complex Systems
Environmental studies present unique challenges. Following a pollutant from, for example, an aerosol phase through groundwater solute and into the food chain via plant matter can be devilishly difficult, and determining its effect of the creatures that consume it more difficult still. Couple that with the fact that some reactions cannot be neatly isolated for reproduction in the lab, and the need for flexible analysis tools becomes clear.
NMR spectroscopy can be and has been used to explore a variety of environmental issues, and has proven useful at looking at both the effects of pollution, and the efficacy of remediation methods. For example, recent research on Mediterranean mussels, a sentinel species, used proton NMR spectroscopy to look at changes in metabolites following exposure to mercury and polycyclic aromatic hydrocarbons, two pollutants release by coal-fired power plants. Proton NMR spectroscopy was also used to assess the viability of iron-based oxidants in remediating tetrachloroethylene and trichloroethylene in soil and groundwater.
NMR spectroscopy also finds many uses in the analysis of organic matter in its many phases. Some examples include:
- Using untreated samples, determine ocean-, lake-, and river-dissolved organic matter at natural abundance. This supplies a snap shot of the environment’s true state to compare with common isolation processes
- Following the germination of a 13C-labelled seed, identifying a wide range of structural and metabolic changes during growth
- Determining soil structure and the interactions between key soil components
- Studying the binding of contaminants in whole soils
- Analyzing a living organism (in this case a tiny crustacean, Hyallala azteca) — in essence, determining the molecular composition of all its components, from solutions through to solids
NMR – A Multiphasic Approach to Environmental Research
To gain a truly comprehensive view of the issues that threaten our planet – and thus our very survival – researchers must be able to track contaminants and the processes they undergo through a wide variety of environments and phases: air, water, soil. Liquid, gel, solid. Advances in comprehensive, multiphase (CMP) NMR spectroscopy enable such a holistic view of systems, and even add insights into more subtle stressors such as climate change through its ability to track an organism’s metabolism. NMR’s capabilities in the areas of in vivo and in situ research make it an indispensable tool for the environmental scientist.
Tracking Free Radicals and Transition Metal Ions in the Environment with EPR
Electron paramagnetic resonance (EPR) spectroscopy is another valuable tool for environmental research, where it is not only used to track free radicals, but can also detect toxic metal ions in groundwater and soil, and follow their uptake by plants. Metal toxicity studies using EPR have been conducted on plants ranging from lichens to lupins. EPR has also been used to examine the mobility and availability of transition metal ions such as copper(II) in soils.