Characterization and source identification of hydrocarbons in water samples using multiple analytical techniques.

This paper describes a case study in which multiple analytical techniques were used to identify and characterize trace petroleum-related hydrocarbons and other volatile organic compounds in groundwater samples collected in a bedrock aquifer exploited for drinking water purposes. The objective of the study was to confirm the presence of gasoline and other petroleum products or other volatile organic pollutants in those samples in order to assess the respective implication of each of the potentially responsible parties to the contamination of the aquifer. In addition, the degree of contamination at different depths in the aquifer was also of interest. The analytical techniques used for analyses of water samples included gas chromatography-mass spectrometry (GC-MS) and capillary GC with flame-ionization detection, solid-phase microextraction and headspace GC-MS techniques. Chemical characterization results revealed the following: (1) The hydrocarbons in sample A (near-surface groundwater, 0-5 m) were clearly of two types, one being gasoline and the other a heavy petroleum product. The significant distribution of five target petroleum-characteristic alkylkated polycyclic aromatic hydrocarbon homologues and biomarkers confirmed the presence of another heavy petroleum product. The concentrations of the TPHs (total petroleum hydrocarbons) and BTEX (collective name of benzene, toluene, ethylbenzene, and p-, m-, and o-xylenes) were determined to be 1070 and 155 microg/kg of water for sample A, respectively. (2) The deepest groundwater (sample B, collected at a depth ranging between 15 and 60 m) was also contaminated, but to a much lesser degree. The concentrations of the TPH and BTEX were determined to be only 130 and 2.6 microg/kg of water for sample B, respectively. (3) The presence of a variety of volatile chlorinated compounds to the groundwater was also clearly identified.

Long-term fate and persistence of the spilled metula oil in a marine salt marsh environment degradation of petroleum biomarkers.

Three coastal sites, heavily oiled from the 1974 Metula oil spill in the Strait of Magellan [two are salt marshes (East and West) and the third, an intertidal asphalt pavement], were examined during May 1998. Complete 'total oil analyses' were performed on the oil samples collected from these sites. Chemical fingerprinting data reveal, except for those samples from the East Marsh untreated plots which were only lightly to moderately weathered, that the spilled oil has undergone significant alteration in chemical composition after 24 years. There are no fundamental differences between the heavily weathered West Marsh and treated East Marsh samples. However, the effect of experimental filling action conducted in 1993 has been to substantially promote plant recolonization. The asphalt pavement samples indicate extremely high degradation of oil hydrocarbons, evidenced by a complete loss of n-alkanes from n-C8 to n-C41 and by depletion of greater than 98% of the alkylated polycyclic aromatic hydrocarbon homologues. Even the most refractory biomarker compounds showed some degree of biodegradation. The biomarkers were generally degraded in the declining order of importance as follows: diasteranes>C27 steranes>tricyclic terpanes>pentacyclic terpanes>norhapanes approximately C29-alphabetabeta-steranes.

Characterization and identification of a "mystery" oil spill from Quebec (1999).

This paper describes a case study in which advanced chemical fingerprinting and data interpretation techniques were used to characterize the chemical compositions and determine the source of an unknown spilled oil from Quebec. On 28 February 1999, significant amounts of oil was reported on the river banks of St. Laurence River in front of a company named "Thermex" (in a town - Beauharnois, Quebec, about 50 km northwest of Montreal). The spilled oil was suspected to be released from a nearby factory. In response to this specific site investigation needs, a tiered analytical approach using GC-MS and GC-flame ionization detection was applied. A variety of diagnostic ratios of "source-specific marker" compounds, in particular isomers of biomarkers and alkylated series of polycyclic aromatic hydrocarbons within the same alkylation groups, were determined and analyzed. The hydrocarbon analysis results reveal the following: (1) the spilled oil is very "specific", and is significantly different from most crude oils in chemical composition; (2) the oil in samples come from the same source, however, the spill sample 2569 was identified to contain a small amount (approximately 10%) of diesel; (3) the spilled oil was relatively "fresh", its chemical composition has not undergone significant alteration yet; (4) the spilled oil showed unusually high concentration of the US Environmental Protection Agency priority polycyclic aromatic hydrocarbons (PAHs). The "Pyrogenic Index" values were determined to be as high as 0.11-0.13, significantly higher than crude oils (<0.010) and heavy Bunker type fuels (0.015-0.060). This indicates significant contribution of PAH composition from pyrogenic components; (5) biomarkers were also detected, but their concentrations were unusually low in comparison to most crude oils.

Comparison of oil composition changes due to biodegradation and physical weathering in different oils.

The well-characterized Alberta Sweet Mixed Blend oil and several other oils which are commonly transported in Canada were physically weathered and then incubated with a defined microbial inoculum. The purpose was to produce quantitative data on oil components and component groups which are more susceptible or resistant to biodegradation, and to determine how oils rank in relation to each other in terms of biodegradation potential. The biodegraded oils were characterized by quantitative determination of changes in important hydrocarbon groups including the total petroleum hydrocarbons, total saturates and aromatics, and also by quantitation of more than 100 individual target aliphatic, aromatic and biomarker components. The study reveals a pattern of distinct oil composition changes due to biodegradation, which is significantly different from the pattern due to physical or short-term weathering. It is important to be able to distinguish between these two forms of loss, so that loss due to weathering is not interpreted as loss due to biodegradation in the laboratory or in the field. Based on these findings, the oil composition changes due to biodegradation can be readily differentiated from those due to physical weathering. To rank the tested oils with respect to biodegradability, losses in total petroleum hydrocarbons and aromatics were used to calculate biodegradation potential indices, employing equations proposed by Environment Canada and the US National Oceanic and Atmospheric Administration. The different methods produced very similar biodegradation trends, confirming that patterns of oil biodegradability do exist.