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Coccolithophores, marine calcifying phytoplankton, are important primary producers impacting the global carbon cycle at different timescales. Their biomineral structures, the calcite containing coccoliths, are among the most elaborate hard parts of any organism. Understanding the morphogenesis of coccoliths is not only relevant in the context of coccolithophore eco-physiology but will also inform biomineralization and crystal design research more generally. The recent discovery of a silicon (Si) requirement for crystal shaping in some coccolithophores has opened up a new avenue of biomineralization research. In order to develop a mechanistic understanding of the role of Si, the presence and localization of this chemical element in coccoliths needs to be known. Here, we document for the first time the uneven Si distribution in Helicosphaera carteri coccoliths through three synchrotron-based techniques employing X-ray Fluorescence and Infrared Spectromicroscopy. The enrichment of Si in specific areas of the coccoliths point to a targeted role of this element in the coccolith formation. Our findings mark a key step in biomineralization research because it opens the door for a detailed mechanistic understanding of the role Si plays in shaping coccolith crystals.

We have investigated the local structure of layered La 1 − x Ce x OBiSSe system by Bi L 3 -edge extended X-ray absorption fine structure (EXAFS) measurements for different Ce substitutions. Ce L 3 -edge X-ray absorption spectroscopy (XAS) has been used to evaluate the Ce valence responsible for the self-doping in this system. We have found that the local distortion, determined by the separation between two Bi-Ch distances within the BiCh 2 -layer (Ch=S,Se), is quickly suppressed by Ce substitution while the axial Bi-S2 bond elongates. Ce L 3 -edge XAS reveals a coexistence of Ce 3 + and Ce 4 + in which the Ce 4 + weight decreases, an indication of a partial breaking of R E -S-Bi ( R E =La/Ce) charge transfer channel with Ce substitution. The results suggest that interaction between R E O spacer layer and BiCh 2 layer, dictated by the out-of-plane Bi-S2 distance, has a significant role in triggering superconductivity in the title system, with the in-plane distortion controlling the charge mobility within the BiCh 2 -layer.

Trees can be successfully used in phytoremediation because of their ability to grow on nutrient-poor soil, deep root system, fast rate of growth, metal-resistance traits and economically viable secondary use. Thanks to these features, trees are able to stabilize, extract, degrade or volatilize soil contaminants. The paper offers a comprehensive review of the role of trees in the phytoremediation of soils contaminated by heavy metals or organic pollutants. Transgenic approaches to enhance the aforementioned processes, together with the use of chelating agents to improve the bioavailability of pollutants for plants uptake, are also reviewed and discussed.