Spatial and temporal trends of polycyclic aromatic hydrocarbons in sediment cores of Brunei Bay, East Malaysia

The spatial and temporal distribution of polycyclic aromatic hydrocarbons (PAHs) in three sediment cores from Brunei Bay, Southern South China Sea was investigated. The total concentrations of 16 priority PAHs (∑PAH16) and their alkyl-substituted derivatives ranged from 10.4 to 376 ng g−1 and 30.7 to 2263 ng g−1, respectively. PAH biomarker diagnostic ratios and principal component analysis (PCA) combined with absolute principal component score (APCS) and multiple linear regression (MLR) were performed to apportion the source contribution. The results revealed mixed inputs of fuel combustion residues and uncombusted petrogenic products. The downcore PAH profile revealed that the highest peaks could be related to past human activities using biofuel and coal during the industrialization/agriculture revolution period. The 1,7/(2,6+1,7)-dimethylphenanthrene ratio also highlighted wood combustion during forest fire outbreaks, which appeared to coincide with the past climate events

Influence of monsoon on the distribution of organic carbon in inner continental shelf core sediments, South China Sea, Malaysia

Three short sediment cores (12-32 cm) from South China Sea off Southern Terengganu were collected during May (post-Northeast monsoon) and September (pre-Northeast monsoon) 2007. The concentration of total organic carbon (TOC) obtained ranged from 0.41-2.23 and 0.38-2.31% during post and pre-monsoon, respectively. TOC concentration was found to decrease with depth and distance from the coast and river mouth. In particular, station with close proximity to the coast exhibits most pronounced variation of TOC with depth. Besides spatial variation, it is noted that the seasonal variations also considerably affect the distribution and concentrations of TOC, where both near and offshore sampling stations showed significant variations in TOC content during May and September sampling. These findings suggest the importance of terrestrial organic carbon flux, physical mixing and seasonal variations in regulating the concentration and distribution of the organic carbon in the study area

Investigation of aliphatic hydrocarbons in core sediments of Brunei Bay, East Malaysia

The distribution of aliphatic hydrocarbons in three sediment cores from Brunei Bay was investigated in order to understand their sources and the biogeochemical processes of these hydrocarbons. The total concentrations of C15 to C37 n-alkanes ranged from 0.70 to 16.5 μg g−1. Traces of hopanes with C29–C31 carbon homologs were detected in the study area. The carbon preference index (CPI15–37) ranged from 1.23 to 3.42 coupled with the natural n-alkane ratio (NAR19–32) ratios (1.52 to 5.34), and the presence of unresolved complex mixtures and hopanes, suggested slight contamination by anthropogenic hydrocarbons, presumably derived from activities along the coasts. The presence of C27 trisnorhopene and diploptene, as well as their association with long-chain and short-chain n-alkanes, revealed a depositional environment of organic matter in the sediment cores

Investigation of aliphatic and polycyclic aromatic hydrocarbons in surface sediments of Brunei Bay, East Malaysia

The surface distributions of aliphatic hydrocarbons and polycyclic aromatic hydrocarbons (PAHs) were investigated from coastal sediments of Brunei Bay, southern South China Sea. The concentrations of total n-alkane (TNA) and 16 USEPA priority PAHs ranged from 0.67 to 9.88 μg/g and 4.72 to 102 ng/g, respectively. Principal component analysis (PCA) clustered the hydrocarbons in surface sediments according to their relationship and geographical locations, anticipated to the inputs and activities in proximity. Biomarker diagnostic ratios revealed that biogenic n-alkane inputs in the coastal sediments are exported from the fluviomarine and mangrove swamp environment, while the PAHs inputs are derived from mixed petrogenic and petroleum combustion residues. Overall, the level of PAHs in the study area is between low to moderate, based on the comparison with other areas worldwide

Input of organic matter in Brunei Bay, East Malaysia, as indicated by sedimentary steroids and multivariate statistics

Brunei Bay is one of the most important marine environments of East Malaysia (South China Sea), covering many productive ecosystems with activities including fisheries, tourism, and main shipping lanes for petroleum transfers. Evaluation of the sources and distributions of steroids in the surface sedimentary organic matter was carried out by gas chromatography–mass spectrometry (GC–MS). The concentrations of the total identified sterols (TIS) ranged between 0.81 and 12.69 μg g−1 dry weight, and the total sterones were between 0.11 and 5.66 μg g−1 dry weight. The coprostanol level was comparatively low (<0.10 μg g−1), and the multi-biomarker proxies indicated that the region did not exhibit significant contamination from sewage effluents. Principal component analysis (PCA) revealed the coastal environment of the study area was dominated by allochthonous (mainly terrestrial) organic matter input

Sources of polycyclic aromatic hydrocarbons in South China Sea short core sediments off Southern part Terengganu, Malaysia and multivariate statistics approaches

Sediment cores from the southern South China Sea off the Terengganu coast were analyzed for polycyclic aromatic hydrocarbons (PAHs) and perylene. The concentrations of total 17 PAH (TPAHs) and perylene varied between 5.45-27.7 ng/g and 0.51-7.77 ng/g, respectively. Analyses of variance showed significant differences between the stations, but not in sub-bottom depths at the 0.05 level. The PAH cross plots showed a predominance of pyrogenic over petrogenic PAHs. Principal component analysis (PCA) showed clustered PAHs that are correlated with total organic carbon (TOC), indicating the importance of surface runoff via fluvial transport for contributing these PAHs to the coastal environment of the study area. Overall, the concentrations of PAHs in the study area are considered to be in the low range, not exceeding the 100 ng/g mark