Detection of mercury and other metals in mercury contaminated soils using mid-infrared spectroscopy

The Oak Ridge Reservation, established in 1942, was the designated site for the construction of the atomic bomb. During a 20-year period from 1944-1963 radioactive and toxic chemical pollutants, especially mercury compounds were released into the surrounding waterways. Mercury in the soil environment can undergo numerous chemical transformations. Conventional methods for detection of total soil mercury in contaminated environments are based on time-consuming sample preparation and costly sample analysis. The possibility for determination of total soil –Hg concentration and other elements in contaminated soils using the mid-infrared (MIR) region (4000 – 600 cm) has been investigated. Principal component analysis (PCA) was used to identify patterns or differences in soil spectral data and partial least squares (PLS) regression was used to develop models for several metals in soil samples. Pearson correlation identified nine elements (Sr, Ni, Cu, Cd, V, Ti, Fe, Ba, Rb) and total carbon that were significantly correlated with total soil-Hg. Our calibration models showed high r for Hg, and Sr (r > .90) and relatively moderate r for Cu and Ni (r > .80). Results support the conclusion that mid-infrared spectroscopy could aid conventional method analyses of soils heavily contaminated with certain heavy metals after a robust model is developed.