Biogeochemical Controls on Latitudinal (42°N to 70°S) and Depth Distribution of Organophosphate Esters in the Atlantic and Southern Oceans

Large-scale oceanic assessments are key for determining the persistence and long-range transport potential of organic pollutants, but there is a dearth of these for organophosphate esters (OPEs), widely used as flame retardants and plasticizers. This work reports the latitudinal distribution (42°N-70°S) and vertical profiles (from the surface to 2000 m depth) of OPEs in the Atlantic and Southern Oceans and explores their biogeochemical controls. The latitudinal gradient shows higher surface OPE concentrations near the equator than at higher latitudes, consistent with the prevailing oceanic and atmospheric circulation, and measured wet deposition events. At the deep chlorophyll maximum depth, there was an inverse correlation between the concentrations of the OPEs and phytoplankton biomass, with the lowest concentrations in the Southern Ocean, consistent with the role of the biological pump depleting the levels of the OPEs from the photic zone. OPE latitudinal trends in the deep ocean (2000 m depth) resembled those at the surface with maximum intertropical concentrations. Analysis derived from OPE concentrations at the bottom of the photic zone and in the minimum oxygen layer suggested a complex dynamic biogeochemical cycling driven by transport, degradation, and redissolution of OPEs with depth. OPEs are persistent enough to reach all oceanic compartments, but a quantitative resolution of the sources, sinks, seasonality, and biogeochemical cycles will require future research.