Characterization of alkanes, hopanes, and polycyclic aromatic hydrocarbons (PAHs) in tar-balls collected from the East Coast of Peninsular Malaysia

Abstract

The East Coast of Peninsular Malaysia faces the South China Sea and is vulnerable to oil pollution because of intense petroleum production activities in the area. The South China Sea is also a favored route for supertankers carrying crude oil to the Far East. Consequently, oil spills can occur, causing pollution and contamination in the surrounding areas. Residual oil spills stranded on coastal beaches usually end up as tar-balls. Elucidating the sources of tar-balls using a molecular marker approach is essential in assessing environmental impacts and perhaps settling legal liabilities for affected parties. This study utilizes a multimodal molecular marker approach through the use of diagnostic ratios of alkanes, hopanes, and polycyclic aromatic hydrocarbons (PAHs) to determine the source, distribution and weathering of tar-balls. Hopane ratios (e.g., C29/C30, and summation C31-C35/C30 ratios) were used to identify the sources of tar-balls. The weathering effects were distinguished by using alkanes, namely the unresolved complex mixture (UCM) and low molecular weight/high molecular weight (L/H) ratios. Similarly, PAHs were also used for the determination of weathering processes undergone by the tar-balls. This multimodal molecular marker gave a very strong indication of the sources of tar-balls in this study. For example, 16 out of 17 samples originated from South East Asian Crude Oil (SEACO) with one sample from Merang, Terengganu originating from North Sea Oil (Troll). The TRME-2 sample may have come from a supertanker's ballast water discharge. The second possibility is that the tar-ball may have been transported via oceanographic currents. All 'weathered' sample characterizations were based on the presence of UCM and other ratios. The multimodal molecular marker approach applied in this study has enabled us to partially understand the transport behavior of tar-balls in the marine environment and has revealed insights into the weathering process of tar-balls.

Evaluation of the diagnostic ratios for the identification of spilled oils after biodegradation

“…Based on this observation, the low molecular weight alkanes (LMW alkanes) (n-C 12 -n-C 21 ) may have undergone microbial degradation compared to the high molecular weight alkanes (HMW alkanes) (n-C 22 -n-C 34 ). Similar distributions were also reported for the tar-balls collected from the East Coast of Peninsular Malaysia (Chandru et al 2008). It is probably because that the biodegradation usually favors the short chained or LMW alkanes compared to longer chained ones.…”

Distributions and source apportionment of sediment-associated polycyclic aromatic hydrocarbons (PAHs) and hopanes in rivers and estuaries of Peninsular Malaysia

“…These characteristics provide potential for hopanes to be used as biomarker. These molecular markers provide a fingerprint to determine the sources of oils (Chandru et al 2008;Saha et al 2009;Volkman et al 1997;Zakaria et al 2002). Hopanes with αβ configuration (e.g., 17α(H),21β(H)-Hopanes) in the C 27 -C 35 range are characteristics of petroleum due to their greater thermodynamic stability compared to those with βα configuration (e.g., 17β(H), 21α(H)-Hopanes) (Sakari et al 2010).…”

Depositional History of Polycyclic Aromatic Hydrocarbons: Reconstruction of Petroleum Pollution Record in Peninsular Malaysia

“…Oleanane is another triterpanes commonly associated with oil derived predominantly from higher plant sources. In conclusion, pentacyclic triterpanes are useful biomarker to identify plant and petroleum input of PAHs into the aquatic environment as well as sediments (Wakeham et al, 1980;Tan and Heit, 1981;Bouloubassi and Saliot, 1993;Yunker and McDonald, 1995;Chandru et al, 2008).…”