Sources of hydrocarbons in sediments of the Mandovi estuary and the Marmugoa harbour, west coast of India

Abstract

Surface sediments were collected from various locations of the Mandovi estuary and the Marmugoa harbour. Sediments were analysed for organic carbon (OC), total lipids, n-alkanes concentration and composition. Concentrations of OC, total lipids and n-alkanes varied spatially and ranged from 1 to 2.5%, 176 to 1413 µg/g dry weight (dw) sediments, and 0.8 to 3.2 µg/g dw sediments of the Mandovi estuary, respectively; and from 0.6 to 2.9%, 233 to 1448 µg/g dw sediments, and 1.6 to 10.7 µg/g dw sediments in the Marmugoa harbour, respectively. Long chain, odd carbon n-alkanes (C 23–C 33) in the Mandovi estuary, whereas short chain, even carbon n-alkanes (C 11–C 21) in the Marmugoa harbour sediments were more abundant. The total HC concentrations, n-alkane composition, CPI, UCM and other evaluation indices suggest the dominance of terrestrial hydrocarbons in the estuarine while petroleum derived hydrocarbons in the harbour sediments. This conclusion was further supported by the abundance of hopanes with C 29 to C 34 α, β compounds and steranes with C 27, C 28 and C 29 compounds in the harbour sediments.