Browsing by Author "Roychoudhury, Alakendra"
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- ItemIron-rich nanoparticles in natural aquatic environments(MDPI, 2019-05-11) Von der Heyden, Bjorn; Roychoudhury, Alakendra; Myneni, SatishNaturally-occurring iron nanoparticles constitute a quantitatively-important and biogeochemically-active component of the broader Earth ecosystem. Yet detailed insights into their chemical speciation is sparse compared to the body of work conducted on engineered Fe nanoparticles. The present contribution briefly reviews the analytical approaches that can be used to characterize natural Fe nanoparticles, before detailing a dedicated synchrotron-based X-ray spectro-microscopic investigation into the speciation of suspended Fe nanoparticles collected from fluvial, marine, and lacustrine surface waters. Ferrous, ferric and magnetite classes of Fe nanoparticles (10–100 nm) were identified, and all three classes exhibited a high degree of heterogeneity in the local bonding environment around the Fe center. The heterogeneity is attributed to the possible presence of nanoparticle aggregates, and to the low degrees of crystallinity and ubiquitous presence of impurities (Al and organic moieties) in natural samples. This heterogeneity further precludes a spectroscopic distinction between the Fe nanoparticles and the larger sized Fe-rich particles that were evaluated. The presented results provide an important baseline for natural nanoparticle speciation in pristine aquatic systems, highlight the degree of inter-particle variability, which should be parameterized in future accurate biogeochemical models, and may inform predictions of the fate of released engineered Fe nanoparticles as they evolve and transform in natural systems.
- ItemSouthern Ocean Seasonal Cycle Experiment 2012 : seasonal scale climate and carbon cycle links(Academy of Science of South Africa, 2012-03-28) Swart, Sebastiaan; Chang, Nicolette; Fauchereau, Nicolas; Joubert, Warren; Lucas, Mike; Mtshali, Thato; Roychoudhury, Alakendra; Tagliabue, Alessandro; Thomalla, Sandy; Waldron, Howard; Monteiro, Pedro M. S.In early May 2012, South Africa will take delivery of a new polar research ship, the SA Agulhas II, representing a significant investment of R1.6 billion in polar infrastructure to further strengthen South Africa’s presence in the polar region, particularly in support of its stewardship of the Southern Ocean and Antarctic Treaty obligations. This investment follows closely on recent DST–CSIR infrastructure investments in the Centre for High Performance Computing, used to run global ocean–climate models, an ocean robotics observational capability and five other new research facilities. Together, these investments offer opportunities to enhance South Africa’s advanced numerical and technological capacity as well as its impact on Southern Hemisphere polar climate and ecosystem science by using its geographical advantage. We are planning the first scientific programme that will capitalise on these major infrastructure investments: the Southern Ocean Seasonal Cycle Experiment (SOSCEx).