Distribution and Source of Hydrocarbons in Marine Sediments from Exclusive Economic Zone (EEZ) off Sarawak, Malaysia.

The concentration and sources of aliphatic hydrocarbons and polycyclic aromatic hydrocarbons (PAHs) in surface and core sediments from Sarawak Exclusive Economic Zone (EEZ) were investigated. Aliphatic hydrocarbons concentrations in surface sediments ranged between 2.8-744.4 μg/g. The highest concentration of total aliphatic hydrocarbons (TAHs) was detected in surface sediment of ST02 (Kuching Waters) with 744.4 μg/g. Concentration of aliphatic hydrocarbons in core sediments ranged between 7.0-123.7, 122.6-324.4 and 8.05-46.6 μg/g of ST01, ST02 and ST03, respectively. The sources of aliphatic hydrocarbons in sediments of Sarawak EEZ were originated from mixture of anthropogenic and biogenic sources as indicated by alkane biomarker indices. Fresh oil input has been detected in sediments at several sites of Sarawak EEZ whereas old petroleum contamination also being observed as indicated by presence of unresolved complex mixture (UCM) and hydrocarbon biomakers (hopane and sterane). Concentrations of PAHs in surface sediments of Sarawak EEZ ranged 8.56-374.7 ng/g. Several sites at Sarawak EEZ were moderately polluted by PAHs but the PAHs concentrations did not pose biological adverse effects because not exceeded the effect range low (ERL) and effect range medium (ERM). Isomeric PAHs ratios were employed to determine sources of PAHs in sediments from Sarawak EEZ. The main source of PAHs in surface sediments of Sarawak EEZ as indicated by Principal Component Analysis (PCA) was pyrogenic. The dominance of high molecular weight (4,5 and 6 ring) PAHs in surface sediments of Sarawak EEZ were correlated with silt and clay fractions. Concentrations of PAHs in core sediments of ST01, ST02 and ST03 were 13.6-92.5, 37.2-151.2 and 24.3-72.9 ng/g, respectively. The presence of unweathered fresh petroleum source was detected in core sediment of ST01. PAHs origin in core sediment of iv ST02 were believed from mixture of pyrogenic and petrogenic with minor input of pyrolytic PAHs. Source of PAHs in core sediment of ST03 was mainly derived from combustion (pyrogenic). Keywords: Aliphatic hydrocarbons; polycyclic aromatic hydrocarbons (PAHs), heavy metals, sediments; Sarawak Exclusive Economic Zone (EE