Source and Distribution of Polycyclic Aromatic Hydrocarbons (PAHs) in Surface Sediment from Chalong Bay, Phuket, Thailand

This study aimed to investigate the spatial distribution and apportionment of potential sources of the 16 US-EPA priority PAHs in surface sediments of Chalong Bay, Phuket, Thailand. A total 28 of sediment samples were collected from areas with high maritime activity in Chalong Bay, subjected to conventional high recovery Soxhlet extraction, purified with SiO2 column chromatography, and quantified by Gas Chromatography-Mass Spectrometry (GC/MS). Total concentration of PAHs (Σ16PAHs) ranged from 31.15 to 1696 ng g−1 dry weight, with an average of 198.2 ± 318.5 ng g−1 dry weight. Binary diagnostic ratios plots were used to distinguish between petrogenic and pyrogenic sources. Most of the PAHs in sediments originated from pyrolytic sources. PCA analysis explained 82.3 % of the variance by only 4 predominant components. The first principal component (PC1) (26.7 %) was mainly contributed to urban street runoff and municipal wastewater discharge. PC2 (25.8 %) represented vehicular combustion sources, PC3 (19.1 %) was attributed to petrogenic sources, and PC4 (10.7 %) was only associated with Naphthalene. The sources of PAHs distributed around Chalong Bay included oil spills, combustion of fossil fuels by shipping, urban street runoff, and municipal wastewater discharge. Each type of sources affected different locations along shores of Chalong Bay. 

Spatial Distribution of Bioavailable Metal Concentrations and Total Metal Concentration-depth Relationship along the Sediment Profile within Phuket Bay

Heavy metals in coastal sediments can adversely affect human health and the environment. The distribution and metal bioavailability of Pb and Zn in 21 sediment samples collected from Phuket Bay, Phuket, Thailand using the first-two steps of sequential extraction proposed by the Standards, Measurements and Testing programme (known as BCR) was determined. The results showed that Pb formed weak complexes contributing up to 11.2% to 33% of its total concentration (1.7 to 7.5 mg kg-1) in the first fraction (BCR1), while Zn in the BCR1 fraction ranged from 4.9% to 9.9%. The results suggest that Pb could easily enter the food chain and the main cause of heavy metal contamination is related to local anthropogenic activities and effects of urbanization in the region, such as the ferry terminal, boatyards, and other maritime activities. Meanwhile, the enrichment factors of the metals showed minor to moderately severe enrichment. The metal concentration-depth relationship along the sediment profile showed metal concen-tration in each layer of the sediment core ranging from 45.4 to 88 mg Zn kg-1 and from 12.7 to 44.5 mg Pb kg-1. Based on the changes in heavy metal accumulation in the sediment core, and the calculated the enrichment factor versus depth, these allowed us to understand the historical variability in pollutant linked to past activities in Phuket Bay

Enhanced light absorption due to the mixing state of black carbon in fresh biomass burning emissions

lack of information on the radiative effects of refractory black carbon (rBC) emitted from biomass burning is a significant gap in our understanding of climate change. A custom-made combustion chamber was used to simulate the open burning of crop residues and investigate the impacts of rBC size and mixing state on the particles' optical properties. Average rBC mass median diameters ranged from 141 to 162 nm for the rBC produced from different types of crop residues. The number fraction of thickly-coated rBC varied from 53 to 64%, suggesting that a majority of the freshly emitted rBC were internally mixed. By comparing the result of observed mass absorption cross-section to that calculated with Mie theory, large light absorption enhancement factors (1.7-1.9) were found for coated particles relative to uncoated cores. These effects were strongly positively correlated with the percentage of coated particles but independent of rBC core size. We suggest that rBC from open biomass burning may have strong impact on air pollution and radiative forcing immediately after their production

Source and Distribution of Polycyclic Aromatic Hydrocarbons (PAHs) in Surface Sediment from Chalong Bay, Phuket, Thailand

This study aimed to investigate the spatial distribution and apportionment of potential sources of the 16 US-EPA priority PAHs in surface sediments of Chalong Bay, Phuket, Thailand. A total 28 of sediment samples were collected from areas with high maritime activity in Chalong Bay, subjected to conventional high recovery Soxhlet extraction, purified with SiO2 column chromatography, and quantified by Gas Chromatography-Mass Spectrometry (GC/MS). Total concentration of PAHs (Σ16PAHs) ranged from 31.15 to 1696 ng g−1 dry weight, with an average of 198.2 ± 318.5 ng g−1 dry weight. Binary diagnostic ratios plots were used to distinguish between petrogenic and pyrogenic sources. Most of the PAHs in sediments originated from pyrolytic sources. PCA analysis explained 82.3 % of the variance by only 4 predominant components. The first principal component (PC1) (26.7 %) was mainly contributed to urban street runoff and municipal wastewater discharge. PC2 (25.8 %) represented vehicular combustion sources, PC3 (19.1 %) was attributed to petrogenic sources, and PC4 (10.7 %) was only associated with Naphthalene. The sources of PAHs distributed around Chalong Bay included oil spills, combustion of fossil fuels by shipping, urban street runoff, and municipal wastewater discharge. Each type of sources affected different locations along shores of Chalong Bay.</jats:p