Environmental Contaminant Detection - EPR (ESR) Applications
Environmental pollution is one of the global crises and is affecting the quality of living and health of the entire population. A new class of harmful substances, the environmentally persistent free radicals (EPFRs). These pollutants are pervasive and can be found in air, water, and soil. The EPFRs can be recognized as biohazard since it can produce reactive oxide species (ROS), which causes cell and tissue damages and ultimately cancer. To mitigate and eventually find a solution to this problem, tracing the origin of such pollutants is needed. Electron paramagnetic resonance (EPR) spectroscopy is a powerful tool and can be used for such tasks. What are EPFRs The conventionally recognized free radicals are often transient with a short lifetime. On the contrary, EPFRs can be stable in the environment for tens of minutes to tens of days without being oxidized or quenched. The commonly found EPFRs include, cyclopentadienyl, semiquinone, phenoxy, and other radicals. Common EPFRs Where do EPFRs come from? EPFRs are found in a wide range of environmental media, such as atmospheric particulate matter (e.g. PM 2.5), factory emissions, tobacco, petroleum coke, wood and plastic, coal combustion particulates, soluble fractions in water bodies, and organically contaminated soils, etc. EPFRs have a wide range of transport pathways in environmental media and can be transported through vertical ascent, horizontal transport, vertical deposition to water bodies, vertical deposition to land, and landward migration of water bodies. In the process of migration, new reactive radicals may be generated, which directly affects the environment and are precursors to other pollutants. Formation and Multimediated Transfer of EPFRs (Environmental Pollution 248 (2019) 320-331) Application of EPR Technique for the Detection of EPFRs EPR spectroscopy is extremely sensitive to unpaired electrons, and a directly measurement of signals from these radicals make it an ideal method for monitoring the presence of EPFRs in different samples. . For the detection of EPFRs, EPR (ESR) spectroscopy provides information in both spatial and temporal dimensions. By measuring and analyzing the continuous-wave EPR spectra of samples, the researchers are able to not only verifying the presence of radicals but also obtain g-values and hyperfine coupling constants of electrons, which can be used for inferring electronic structure of measured molecules. The temporal resolution refers to the half-life of EPFRs, which can also be obtained from monitoring their EPR signals over time. Application of EPR Technology in Detecting EPFRs in the Soil Environment Petroleum processing, storage, transportation, and possible leakage from storage tanks are all susceptible to soil contamination. Although thermal treatment techniques can be used to remediate soils contaminated by various volatile, semi-volati...