title: (234)Th as a tracer of vertical transport of polycyclic aromatic hydrocarbons in the northern Gulf of Mexico.
abstract: Particle-mediated vertical flux of polycyclic aromatic hydrocarbons (PAHs) plays an important role in their removal from upper oceans and sets a limit on the amount delivered to the deep-sea sediments. In this study, we applied a one-dimensional steady-state (234)Th scavenging model to estimate vertical flux of PAHs in the northern Gulf of Mexico and compared them with sediment trap based flux estimates. The (234)Th-based ∑PAH43 fluxes were 6.7±1.0μgm(-2)d(-1) and 3.7±0.6μgm(-2)d(-1) while sediment trap-based fluxes were 4.0±0.6μgm(-2)d(-1) and 4.5±0.7μgm(-2)d(-1) at 150m and 250m, respectively. Alkylated homologues contributed to 80% of the total PAH fluxes which is in contrary to other regions where combustion derived parent PAHs dominate the fluxes. The results indicate that the (238)U-(234)Th disequilibria can be an effective tracer of particulate PAH fluxes in upper mesopelagic zones and can provide flux estimates with high spatial coverage needed to quantify their long term fate and transport in the marine systems.
authors.affiliation: Department of Oceanography and Coastal Sciences, Louisiana State University, 1143 ECE Building, Baton Rouge, LA 70803, United States; Department of Environmental Sciences, Louisiana State University, 1257 ECE Building, Baton Rouge, LA 70803, United States. Electronic address: padhik2@lsu.edu.
authors.forename: Puspa L
authors.initials: PL
authors.lastname: Adhikari
authors.affiliation: Department of Oceanography and Coastal Sciences, Louisiana State University, 1143 ECE Building, Baton Rouge, LA 70803, United States.
authors.forename: Kanchan
authors.initials: K
authors.lastname: Maiti
authors.affiliation: Department of Oceanography and Coastal Sciences, Louisiana State University, 1143 ECE Building, Baton Rouge, LA 70803, United States.
authors.forename: Somiddho
authors.initials: S
authors.lastname: Bosu
authors.affiliation: Department of Oceanography and Coastal Sciences, Louisiana State University, 1143 ECE Building, Baton Rouge, LA 70803, United States.
authors.forename: Patrick R
authors.initials: PR
authors.lastname: Jones
mesh_terms: D004784:Environmental Monitoring / Q000379:methods*; D019015:Geologic Sediments; D060851:Gulf of America; D008800:Mexico; D008956:Models, Chemical; D009792:Oceans and Seas; D011084:Polycyclic Aromatic Hydrocarbons / Q000032:analysis*; D013910:Thorium / Q000032:analysis; D014874:Water Pollutants, Chemical / Q000032:analysis*
chemical_list: D011084:Polycyclic Aromatic Hydrocarbons; D014874:Water Pollutants, Chemical; D013910:Thorium
keywords: (238)U–(234)Th disequilibria; Gulf of Mexico; Particulate PAH fluxes; Polycyclic aromatic hydrocarbons (PAHs); Sediment traps; Vertical transport fluxes