title: Sources of sedimentary PAHs in tropical Asian waters: differentiation between pyrogenic and petrogenic sources by alkyl homolog abundance.
abstract: We collected surface sediment samples from 174 locations in India, Indonesia, Malaysia, Thailand, Vietnam, Cambodia, Laos, and the Philippines and analyzed them for polycyclic aromatic hydrocarbons (PAHs) and hopanes. PAHs were widely distributed in the sediments, with comparatively higher concentrations in urban areas (Sigma PAHs: approximately 1000 to approximately 100,000 ng/g-dry) than in rural areas ( approximately 10 to approximately 100g-dry), indicating large sources of PAHs in urban areas. To distinguish petrogenic and pyrogenic sources of PAHs, we calculated the ratios of alkyl PAHs to parent PAHs: methylphenanthrenes to phenanthrene (MP/P), methylpyrenes+methylfluoranthenes to pyrene+fluoranthene (MPy/Py), and methylchrysenes+methylbenz[a]anthracenes to chrysene+benz[a]anthracene (MC/C). Analysis of source materials (crude oil, automobile exhaust, and coal and wood combustion products) gave thresholds of MP/P=0.4, MPy/Py=0.5, and MC/C=1.0 for exclusive combustion origin. All the combustion product samples had the ratios of alkyl PAHs to parent PAHs below these threshold values. Contributions of petrogenic and pyrogenic sources to the sedimentary PAHs were uneven among the homologs: the phenanthrene series had a greater petrogenic contribution, whereas the chrysene series had a greater pyrogenic contribution. All the Indian sediments showed a strong pyrogenic signature with MP/P approximately 0.5, MPy/Py approximately 0.1, and MC/C approximately 0.2, together with depletion of hopanes indicating intensive inputs of combustion products of coal and/or wood, probably due to the heavy dependence on these fuels as sources of energy. In contrast, sedimentary PAHs from all other tropical Asian cities were abundant in alkylated PAHs with MP/P approximately 1-4, MPy/Py approximately 0.3-1, and MC/C approximately 0.2-1.0, suggesting a ubiquitous input of petrogenic PAHs. Petrogenic contributions to PAH homologs varied among the countries: largest in Malaysia whereas inferior in Laos. The higher abundance of alkylated PAHs together with constant hopane profiles suggests widespread inputs of automobile-derived petrogenic PAHs to Asian waters.
authors.affiliation: Tokyo University of Agriculture and Technology, Fuchu, Tokyo 183-8509, Japan.
authors.forename: Mahua
authors.initials: M
authors.lastname: Saha
authors.forename: Ayako
authors.initials: A
authors.lastname: Togo
authors.forename: Kaoruko
authors.initials: K
authors.lastname: Mizukawa
authors.forename: Michio
authors.initials: M
authors.lastname: Murakami
authors.forename: Hideshige
authors.initials: H
authors.lastname: Takada
authors.forename: Mohamad P
authors.initials: MP
authors.lastname: Zakaria
authors.forename: Nguyen H
authors.initials: NH
authors.lastname: Chiem
authors.forename: Bui Cach
authors.initials: BC
authors.lastname: Tuyen
authors.forename: Maricar
authors.initials: M
authors.lastname: Prudente
authors.forename: Ruchaya
authors.initials: R
authors.lastname: Boonyatumanond
authors.forename: Santosh Kumar
authors.initials: SK
authors.lastname: Sarkar
authors.forename: Badal
authors.initials: B
authors.lastname: Bhattacharya
authors.forename: Pravakar
authors.initials: P
authors.lastname: Mishra
authors.forename: Touch Seang
authors.initials: TS
authors.lastname: Tana
mesh_terms: D001208:Asia; D004784:Environmental Monitoring; D019015:Geologic Sediments / Q000737:chemistry*; D009792:Oceans and Seas; D011084:Polycyclic Aromatic Hydrocarbons / Q000032:analysis* / Q000737:chemistry*; D012015:Reference Standards; D014329:Tropical Climate; D014874:Water Pollutants, Chemical / Q000032:analysis* / Q000737:chemistry*
chemical_list: D011084:Polycyclic Aromatic Hydrocarbons; D014874:Water Pollutants, Chemical