Distribution of geochemical blomarkers in the core sediments of Santubong and Sarawak rivers

Bebe Norlita, Mohamed. (2009) Distribution of geochemical blomarkers in the core sediments of Santubong and Sarawak rivers. Masters thesis, Universiti Malaysia Sarawak (UNIMAS).

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Abstract

The extent of pollution at Santubong and Sarawak Rivers was determined by analyzing the geochemical biomarkers in the core sediments. The distribution of aliphatic hydrocarbons and polycyclic aromatic hydrocarbons (PAHs) in the core sediments was determined qualitatively and quantitatively while the distribution of sterols, fatty acid methyl esters (FAMEs) and phthalates was determined qualitatively. The core sediments were Soxhlet extracted for 12 hours using dichloromethane to obtain the geolipids. Subsequently, the geolipids were fractionated into 5 fractions using activated silica gel column chromatography. The aliphatic and aromatic hydrocarbon fractions were analyzed on capillary gas chromatography/flame ionization detector (GC/FID) while polar fractions, FAMES, phthalate esters and alcohols, were analyzed on gas chromatography/mass spectrometry (GC/MS). Total organic matter in the core sediments from Santubong and Sarawak rivers varied from 3.44 - 7.07 % and 2.03 - 6.55 %, respectively. Core sediments from both rivers showed the presence of unresolved complex mixture eluting between Cis to C34. The total n-alkanes in core sediments from Santubong and Sarawak rivers ranged from 10.8 - 101.1 µg/g dw and 7.3 - 61.7 gg/g dw, respectively. Pristane/C17 and phytane/C18 suggest low degradation of aliphatic hydrocarbons. Biomarker indices of total n-alkanes indicated a mixture of inputs from both biogenic and petrogenic sources. Total PAHs in core sediments from Santubong and Sarawak rivers ranged from 0.8 - 2.5 µg/g dw and 0.7 - 6.7 µg/g dw, respectively. The PAHs ratios including fluoranthene/pyrene and benzo[ajanthracene/chrysene showed the PAHs originated from pyrolitic inputs. Both Santubong and Sarawak Rivers are considered moderately polluted with n-alkanes and PAHs of anthropogenic natures. Domination of short chain FAMEs 111 (< C2o) in core sediments from both rivers indicates planktonic sources of FAMES. Phthalate esters which are widely used as plasticizers were also detected in core sediments from both rivers. The core sediments from both rivers were also dominated by short chain alcohols and sterols (< C22) that indicates inputs from unspecified marine, terrestrial and bacterial origins.

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