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Abstract
Over the past decade, Chini Lake has experienced tremendous changes due to land conversions from forest to agriculture such as oil palm and rubber plantations and also construction of a small barrage downstream of the Chini River. This land conversion has caused changes to the plant community and increased sedimentation rates in the lake. Consequently, this study was carried out to investigate the distribution patterns and sources of n-alkanes in four sediment core samples from Chini Lake and to evaluate the relative changes in organic matter inputs from land and lake flora. In the long-chain n-alkanes (LHC > C23)region, carbon preference index (CPI) values ranged from 1–1.52 in the sediment cores. Most lake sediments analyzed did not contain an unresolved complex mixture (UCM). The average nC17/pristane ratios (nC17/Pr) were 5.34 ± 1.99 and the average nC18/phytane (nC18/Ph) ratios were 1.27 ± 0.25 for the sediment profiles. The n-alkane average chain length (ACL) was 29.68 ± 0.15in the study area. There was significant positive correlation between ACL and CPI in the sediment cores at station B (r = 0.769, p = 0.003), station C (r = 0.735, p = 0.015), station D (r = 0.737, p = 0.006), and station E (r = 0.741, p = 0.006). Positive correlations between diploptene and long-chain n-alkanes (nC25−nC33) were found for sediment core B (r = 0.976, p<0.001), sediment core C (r = 0.836, p = 0.003), sediment core D (r = 0.824, p = 0.001) and sediment core E (r = 0.865, p < 0.001). Terrigenious to aquatic ratio for hydrocarbons (TARHC) and total n-alkanes (∑HC) concentrations increased with depth a pattern that contrast with short chain n-alkanes/total organic carbon (SHC/TOC) ratios. It can be concluded that the petrogenic hydrocarbon contamination in the sediment cores is minimal and that the n-alkanes preserved in Chini Lake sediments are influenced by higher plant waxes and bacteria.