Summary of Abstract Submission

Abstract Submission No. IO50-03-0009PresentationPoster

CHARACTERISTICS AND WEATHERING PATTERN OF THE TAR BALLS (OIL RESIDUES) DEPOSITED ALONG THE WEST COAST OF INDIA AND THEIR ORIGIN

SUNEEL VASIMALLA*1, P. VETHAMONY1, BG NAIK1

1 CSIR-NATIONAL INSTITUTE OF OCEANOGRAPHY, INDIA

ABSTRACT :

Oil residues in the form of tar balls have been depositing along the west coast of India (off Gujarat, Mumbai, Ratnagiri, Goa and Karwar) since 1970s. However, in recent years, this problem has become more consistent, and the stakeholders are concerned about this environmental issue. We are monitoring the tar ball deposition since 2010, and it is found that in the years 2011, 2012, 2013 and 2014 the deposition has become very significant along the Goa coast. Since there was no tanker accidents, other than MSC Chitra in 2010 off Mumbai, the source could be either tanker washes (along the international tanker routes) or offshore oil fields (located off Mumbai-Gujarat). The objectives of this study are: (i) to study the characteristics (color, size, density and buoyancy) of tar balls, (ii) to understand the weathering pattern of the tar balls and (iii) to identify the source oil. In the present study, we have analyzed the tar ball samples collected along the Gujarat coast during 2013 and crude oil samples collected from the Bombay High (BHM, BHH), Cairn and Niko oil fields. We have also used published data of other crude oils (Eg. Middle East and South East crude oils). The results of n-alkane, and EPA-polycyclic aromatic hydrocarbons were used to study the weathering pattern. The results show that the tar ball samples collected from the Gujarat coast have been weathered in various degrees and the status of weathering was moderate. The analysis of pentacyclic triterpanes (hopanes) and their diagnostic ratios reveal that the source of Gujarat tar balls is Bombay High (BH); the compound specific isotope analysis also confirmed the same.