Petroleum Contamination Characterization and Quantification Using Fluorescence Emission-Excitation Matrices (EEMs) and Parallel Factor Analysis (PARAFAC)

Article excerpt

Abstract: This paper introduces a novel approach to characterize and semi-quantify common petroleum contaminants (natural gas condensate, gasoline, diesel, flare pit residue, and heavy crude oil) and their underlying aromatic hydrocarbon components in solutions based on their fluorescence spectral signatures. The method uses fluorescence excitation-emission matrices (EEMs) combined with multivariate statistical procedures: parallel factor analysis (PARAFAC) and soft independent method of class analogy (SIMCA) to identify the petroleum products. Quantitatively, fluorescence intensities of EEMs of analyzed petroleum products at different concentrations are used to establish standard calibration curves that can be employed to estimate unknown concentrations of similar petroleum products in solutions. As well, underlying aromatic hydrocarbon component concentrations are estimated by performing customized PARAFAC analysis. This approach provides fingerprints for different petroleum products along with estimates of their concentrations in non-fluorescing solvents. Concentrations of predicted PARAFAC components were validated by laboratory chemical analytical results of the same petroleum products.

Key words: petroleum, hydrocarbons, aromatic, fluorescence, geo-environmental, contamination, fluorescence emission-excitation matrices, EEMs, parallel factor analysis, PARAFAC, SIMCA.

Resume : Cet article presente une nouvelle approche visant a caracteriser et a partiellement quantifier les contaminants petroliers communs (condensat de gaz naturel, essence, diesel, residus de fosses de brulage et petrole brut lourd) et leurs composantes hydrocarbures aromatiques dans des solutions basees sur leur spectre de fluorescence. La methode utilise des matrices d'excitation-emission de fluorescence (EEM) combinees a des procedures statistiques a multiples variables : l'analyse factorielle parallele (PARAFAC) et une methode douce independante d'analogie de classe (SIMCA) afin d'identifier les produits petroliers. De maniere quantitative, les intensites de fluorescence des EEM provenant des produits petroliers analyses a differentes concentrations sont utilisees pour etablir les courbes d'etalonnage normales utilisees pour estimer des concentrations inconnues de produits petroliers semblables en solution. De plus, les concentrations des composantes hydrocarbures aromatiques sont estimees en realisant une analyse PARAFAC sur mesure. Cette approche fournit les empreintes des differents produits petroliers et des estimations de leur concentration dans des solvants non fluorescents. Les concentrations prevues des composantes PARAFAC ont ete validees par les resultats d'analyse chimique en laboratoire sur les memes produits petroliers.

Mots-cles : petrole, hydrocarbures, aromatiques, fluorescence, geoenvironnemental, contamination, matrices d'excitatione-mission de fluorescence, EEM, analyse factorielle parallele, PARAFAC, SIMCA.

[Traduit par la Redaction]

Introduction

Polycyclic aromatic hydrocarbons (PAHs) in petroleum products are considered as significant environmental pollutants; therefore, reliable analytical methods for detecting and characterizing these compounds in environmental solution or soil samples are of great interest (Bjorseth and Ramdahl 1985). Existing petroleum contaminants characterization and identification methods involves initial screening in the field, then carefully obtaining samples in the field and having them analyzed in a distant laboratory, which is an expensive and time-consuming procedure. Fluorescence spectroscopy is an efficient screening method that could complement current screening methods and may be used directly on various types of environmental samples because it does not require any pre-separation steps, and has been used successfully to detect petroleum products at contaminated sites. The use of fluorescence spectroscopy as a detection technique to determine PAHs in marine sediments was applied successfully to detect freshly spilled crude oil in a marine environment (Vandermeulen et al. …