Heavy Metals and Hydrocarbon Distribution Characteristics of Sediments from Batang Sadong of Samarahan Division, Sarawak, Malaysia

Omorinoye, Omolayo Ajoke (2020) Heavy Metals and Hydrocarbon Distribution Characteristics of Sediments from Batang Sadong of Samarahan Division, Sarawak, Malaysia. PhD thesis, Universiti Malaysia Sarawak (UNIMAS).

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Abstract

Sediments are useful tools in understanding the environmental processes. The physical and chemical characteristics of sediments are dependent on geology, hydrological factors, geochemical influences, human activities and others. Sadong River is a major river catchment in Sarawak and the characteristics of the river sediments can be influenced by natural and anthropogenic factors. The aim of this study was to describe the sedimentological features of the river, and also determine the spatial and vertical distribution of heavy metals as well as the hydrocarbons. The degree of contamination by heavy metals and hydrocarbon compounds in the sediments were assessed. The surface sediments and core sediments with depths between 25 – 45 cm from seven sampling locations along Batang Sadong of Samarahan Division, Sarawak have been studied. The surface and core sediments were subjected to sedimentological analysis to determine the grain size distribution, moisture content, total organic matter (TOM) and ash content. Geochemical analyses were also conducted to determine the heavy metal and hydrocarbon contents in sediments. Heavy metals were extracted by wet digestion using a mixture of HNO3:HCl (3:1; v/v) and then analysed using atomic absorption spectrophotometer (AAS). Concentration of the eight (8) heavy metals and three (3) major metals in surface sediments were determined. The concentration of heavy metals in surface sediments were ranged 19.2 to 46.61 mg/kg (Zn), 3.45 to 12.30 mg/kg (Cu), 219.59 to 464.75 mg/kg (Mn), 1801.85 to 3447.62 mg/kg (Fe); 3.71 to 18.63 mg/kg (As) and 4.61 to 69.73 mg/kg (Pb). The geoaccumulation index (Igeo), contamination factor (CF) and enrichment factor (EF) showed that the surface sediments of Sadong River is unpolluted. Both principal component analysis (PCA) and cluster analysis (CA) showed the heavy metals were mainly derived from lithogenic sources with minimal input from anthropogenic sources. The concentration of Fe in core sediments was consistent from the upper layer to lower layer for all cores. The concentration of Cu in core sediments was consistent for all samples except for Sungai Buloh (BS3). Distribution pattern of Ni, Zn and Mn varied from the upper to the lower layers of core with a fluctuated pattern. Both aliphatic and aromatic hydrocarbons in the surface and core sediments were analysed using Gas Chromatography-Mass Spectrometry (GC-MS). Domination of n-alkanes originated from vascular plants were observed with significance high molecular weight (HMW) n-alkanes with odd carbon numbers in the sediments. Data of average chain length (ACL) and carbon preference index (CPI) supported this finding as observed in Sadong Jaya (BS2) and Serian (BS7). Terrigenous aquatic ratio (TAR) showed the importance of terrestial plant over biogenic n-alkanes in the sediments. The LMW/HMW (value <1) showed domination of HMW n-alkanes in all sediment samples except for Sadong Jaya (BS2) sediment with a value 1.07. The presence of n-alkanes in the sediments of Sadong River may be associated with minimal petroleum input through direct deposition into the sediments or indirect ways by land runoff. Assessment of n-alkanes in the core sediment showed the hydrocarbons originated from terrestial vascular plants, phytoplankton, algae and petroleum. Sixteen (16) targeted PAHs have been detected in Sadong River sediments with the occurrence of pyrene and fluoranthene which indicated pyrolytic input. The distribution and environmental indices of heavy metals and hydrocarbons showed sediments of Sadong River are unpolluted with heavy metals and hydrocarbons which are derived mainly from natural and minimal input of anthropogenic sources.

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