The effect of pH, grain size, and organic ligands on biotite weathering rates

Biotite dissolution rates were determined at 25 °C, at pH 2–6, and as a function of mineral composition, grain size, and aqueous organic ligand concentration. Rates were measured using both open- and closed-system reactors in fluids of constant ionic strength. Element release was non-stoichiometric and followed the general trend of Fe, Mg > Al > Si. Biotite surface area normalised dissolution rates (ri) in the acidic range, generated from Si release, are consistent with the empirical rate law: ri=kH,iaxiH+ where kH,i refers to an apparent rate constant, aH+ designates the activity of protons, and xi stands for a reaction order with respect to protons. Rate constants range from 2.15 × 10−10 to 30.6 × 10−10 (molesbiotite m−2 s−1) with reaction orders ranging from 0.31 to 0.58. At near-neutral pH in the closed-system experiments, the release of Al was stoichiometric compared to Si, but Fe was preferentially retained in the solid phase, possibly as a secondary phase. Biotite dissolution was highly spatially anisotropic with its edges being ∼120 times more reactive than its basal planes. Low organic ligand concentrations slightly enhanced biotite dissolution rates. These measured rates illuminate mineral–fluid–organism chemical interactions, which occur in the natural environment, and how organic exudates enhance nutrient mobilisation for microorganism acquisition

The role of forest trees and their mycorrhizal fungi in carbonate rock weathering and its significance for global carbon cycling

On million-year timescales, carbonate rock weathering exerts no net effect on atmospheric CO2 concentration. However, on timescales of decades-to-centuries, it can contribute to sequestration of anthropogenic CO2 and increase land–ocean alkalinity flux, counteracting ocean acidification. Historical evidence indicates this flux is sensitive to land use change, and recent experimental evidence suggests that trees and their associated soil microbial communities are major drivers of continental mineral weathering. Here, we review key physical and chemical mechanisms by which the symbiotic mycorrhizal fungi of forest tree roots potentially enhance carbonate rock weathering. Evidence from our ongoing field study at the UK's national pinetum confirms increased weathering of carbonate rocks by a wide range of gymnosperm and angiosperm tree species that form arbuscular (AM) or ectomycorrhizal (EM) fungal partnerships. We demonstrate that calcite-containing rock grains under EM tree species weather significantly faster than those under AM trees, an effect linked to greater soil acidification by EM trees. Weathering and corresponding alkalinity export are likely to increase with rising atmospheric CO2 and associated climate change. Our analyses suggest that strategic planting of fast-growing EM angiosperm taxa on calcite- and dolomite-rich terrain might accelerate the transient sink for atmospheric CO2 and slow rates of ocean acidification

The bio-inorganic interface : interaction of ectomycorrhizal fungi and exudates with silicate minerals

EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Towards a general architecture for social media data capture from a multi-domain perspective

Online Social Media (OSM) platforms, such as Facebook or Twitter, are part of everyday life as powerful communication tools. They let users communicate anywhereanytime, and improve their own public image. For this reason, OSM are becoming more and more popular. Social Media data may play a crucial role in various decision-making processes. In this setting, research topics connected to monitoring of Social Media data are becoming increasingly important. The presented work is grounded on direct extensive experiences in data collection from different Social Media sources, and on the different methodologies applied in different reference domains (namely Online Reputation, Social Media Intelligence, and Opinion Mining in tourism). The crawlers developed for these domains provide valuable suggestions to elicit diverse requirements. After lessons learned in such fields, a general architecture for data capture from Social Media sources has been devised, and the interfaces of the composing modules have been defined. The resulting API can be exploited for an orderly re-engineering of crawling tools in the reference domains, thus implementing specific versions of the generic architecture

Routes of phlogopite weathering by three fungal strains

publisher: Elsevier articletitle: Routes of phlogopite weathering by three fungal strains journaltitle: Fungal Biology articlelink: http://dx.doi.org/10.1016/j.funbio.2016.08.007 content_type: article copyright: © 2016 British Mycological Society. Published by Elsevier Ltd. All rights reserved.© 2016 British Mycological Society. Published by Elsevier Ltd. All rights reserved. The attached document is the author's final accepted version of the journal article. You are advised to consult the publisher's version if you wish to cite from it

Atomic-resolution three-dimensional hydration structures on a heterogeneously charged surface

Local hydration structures at the solid-liquid interface around boundary edges on heterostructures are key to an atomic-level understanding of various physical, chemical and biological processes. Recently, we succeeded in visualising atomic-scale three-dimensional hydration structures by using ultra-low noise frequency-modulation atomic force microscopy. However, the time-consuming three-dimensional-map measurements on uneven heterogeneous surfaces have not been achieved due to experimental difficulties, to the best of our knowledge. Here, we report the local hydration structures formed on a heterogeneously charged phyllosilicate surface using a recently established fast and nondestructive acquisition protocol. We discover intermediate regions formed at step edges of the charged surface. By combining with molecular dynamics simulations, we reveal that the distinct structural hydrations are hard to observe in these regions, unlike the charged surface regions, possibly due to the depletion of ions at the edges.Our methodology and findings could be crucial for the exploration of further functionalities.Peer reviewe