title: Examining (239+240)Pu, (210)Pb and historical events to determine carbon, nitrogen and phosphorus burial in mangrove sediments of Moreton Bay, Australia.
abstract: Two sediment cores were collected in a mangrove forest to construct geochronologies for the previous century using natural and anthropogenic radionuclide tracers. Both sediment cores were dated using (239+240)Pu global fallout signatures as well as (210)Pb, applying both the Constant Initial Concentration (CIC) and the Constant Rate of Supply (CRS) models. The (239+240)Pu and CIC model are interpreted as having comparable sediment accretion rates (SAR) below an apparent mixed region in the upper ∼5 to 10 cm. In contrast, the CRS dating method shows high sediment accretion rates in the uppermost intervals, which is substantially reduced over the lower intervals of the 100-year record. A local anthropogenic nutrient signal is reflected in the high total phosphorus (TP) concentration in younger sediments. The carbon/nitrogen molar ratios and δ(15)N values further support a local anthropogenic nutrient enrichment signal. The origin of these signals is likely the treated sewage discharge to Moreton Bay which began in the early 1970s. While the (239+240)Pu and CIC models can only produce rates averaged over the intervals of interest within the profile, the (210)Pb CRS model identifies elevated rates of sediment accretion, organic carbon (OC), nitrogen (N), and TP burial from 2000 to 2013. From 1920 to 2000, the three dating methods provide similar OC, N and TP burial rates, ∼150, 10 and 2 g m(-2) year(-1), respectively, which are comparable to global averages.
authors.affiliation: National Marine Science Centre, School of Environment, Science and Engineering, Southern Cross University, PO Box 4321, Coffs Harbour, 2450 NSW, Australia. Electronic address: christian.sanders@scu.edu.au.
authors.forename: Christian J
authors.initials: CJ
authors.lastname: Sanders
authors.affiliation: National Marine Science Centre, School of Environment, Science and Engineering, Southern Cross University, PO Box 4321, Coffs Harbour, 2450 NSW, Australia.
authors.forename: Isaac R
authors.initials: IR
authors.lastname: Santos
authors.affiliation: Centre for Coastal Biogeochemistry Research, School of Environment, Science and, Engineering, Southern Cross University, Lismore, New South Wales, Australia.
authors.forename: Damien T
authors.initials: DT
authors.lastname: Maher
authors.affiliation: College of Marine Science, University of South Florida, St. Petersburg, Florida, USA.
authors.forename: Joshua L
authors.initials: JL
authors.lastname: Breithaupt
authors.affiliation: Department of Environmental Science, Policy, and Geography, University of South Florida, St. Petersburg, Florida, USA.
authors.forename: Joseph M
authors.initials: JM
authors.lastname: Smoak
authors.affiliation: Department of Chemistry, Metropolitan State University of Denver, Denver, Colorado, USA.
authors.forename: Michael
authors.initials: M
authors.lastname: Ketterer
authors.affiliation: Centre for Coastal Biogeochemistry Research, School of Environment, Science and, Engineering, Southern Cross University, Lismore, New South Wales, Australia.
authors.forename: Mitchell
authors.initials: M
authors.lastname: Call
authors.affiliation: School of Environment, Science and Engineering, Southern Cross University GeoScience, Lismore, New South Wales, Australia.
authors.forename: Luciana
authors.initials: L
authors.lastname: Sanders
authors.affiliation: Centre for Coastal Biogeochemistry Research, School of Environment, Science and, Engineering, Southern Cross University, Lismore, New South Wales, Australia.
authors.forename: Bradley D
authors.initials: BD
authors.lastname: Eyre
mesh_terms: D061006:Bays / Q000032:analysis; D002244:Carbon / Q000032:analysis*; D019015:Geologic Sediments / Q000737:chemistry*; D007856:Lead Radioisotopes / Q000032:analysis*; D009584:Nitrogen / Q000032:analysis*; D010758:Phosphorus / Q000032:analysis*; D011005:Plutonium / Q000032:analysis*; D011793:Queensland; D011847:Radioactive Fallout / Q000032:analysis*; D055110:Radiometric Dating; D053833:Wetlands
chemical_list: D007856:Lead Radioisotopes; D011847:Radioactive Fallout; D010758:Phosphorus; D011005:Plutonium; D002244:Carbon; D009584:Nitrogen
keywords: Carbon accumulation; Geochronology; Impacted mangroves; Lead-210; Plutonium-239+240