Oil spill in northeastern Brazil: Application of fluorescence spectroscopy and PARAFAC in the analysis of oil-related compounds

Between November 2019 and February 2020, 53 water samples were collected along 430 km of coastline in northeastern Brazil, which was the location of an oil spill that occurred in August 2019. Synchronous fluorescence matrices (SFMs) were acquired to avoid regions affected by Raman Stokes scatterings and second harmonic signals, and then, the SFMs were converted into excitation-emission matrices (EEM) by shear transformation. The matrix coupled with parallel factor analysis (PARAFAC) was used in the study of fluorescent components present in the collected waters. A sample collected before the oil spill and another from Florianópolis-SC, 2000 km from the incident, were used as references for nonimpacted waters. In the postspill samples, 4 components were determined, with component 1 (λ_exc = 225 nm, λ_em = 475 nm) being associated with humic-like organic matter (terrestrial), component 2 (λ_exc = 230 nm, λ_em = 390 nm) being associated with humic-like organic matter (marine), component 3 (λ_exc = 225/295 nm, λ_em = 345 nm) being associated with dibenzothiophene-like components also observed in tests with crude oil samples, and component 4 (λ_exc = 220/280 nm, λ_em = 340 nm) being associated with a naphthalene-like substance. Principal component analysis (PCA) was performed on the PARAFAC scores. The distribution of samples along the 4 components was observed and compared with the reference samples.