Removal of emerging persistent organic pollutants (Em-POPs) model compounds from water using a natural porous material functionalized with graphene-based products

This study focuses on the removal of three model compounds, classified as emerging persistent organic pollutants (Em-POPs), from water using a modified version of natural Australian zeolite. Following a series of subsequent treatments and vacuum deposition of graphene oxide (GO), both chemical and physical properties of the adsorbent were characterized. The GO-coated zeolite was tested for the removal of methylene blue (MB), disperse blue 26 (DB26), and sodium fluorescein (NaFn). Results show excellent removal capability for MB and DB26 dyes and decent removal for NaFn when compared to commercially available products such as granular activated carbon. Regeneration of the adsorbent showed virtually no loss in adsorptive performance after two cycles, with MB and DB26.

Shallow particulate organic carbon regeneration in the South Pacific Ocean

Particulate organic carbon (POC) produced in the surface ocean sinks through the water column and is respired at depth, acting as a primary vector sequestering carbon in the abyssal ocean. Atmospheric carbon dioxide levels are sensitive to the length (depth) scale over which respiration converts POC back to inorganic carbon, because shallower waters exchange with the atmosphere more rapidly than deeper ones. However, estimates of this carbon regeneration length scale and its spatiotemporal variability are limited, hindering the ability to characterize its sensitivity to environmental conditions. Here, we present a zonal section of POC fluxes at high vertical and spatial resolution from the GEOTRACES GP16 transect in the eastern tropical South Pacific, based on normalization to the radiogenic thorium isotope 230Th. We find shallower carbon regeneration length scales than previous estimates for the oligotrophic South Pacific gyre, indicating less efficient carbon transfer to the deep ocean. Carbon regeneration is strongly inhibited within suboxic waters near the Peru coast. Canonical Martin curve power laws inadequately capture POC flux profiles at suboxic stations. We instead fit these profiles using an exponential function with flux preserved at depth, finding shallow regeneration but high POC sequestration below 1,000 m. Both regeneration length scales and POC flux at depth closely track the depths at which oxygen concentrations approach zero. Our findings imply that climate warming will result in reduced ocean carbon storage due to expanding oligotrophic gyres, but opposing effects on ocean carbon storage from expanding suboxic waters will require modeling and future work to disentangle.