Forested ecosystems diversified more than 350 Ma to become major engines of continental silicate weathering, regulating the Earth's atmospheric carbon dioxide concentration by driving calcium export into ocean carbonates. Our field experiments with mature trees demonstrate intensification of this weathering engine as tree lineages diversified in concert with their symbiotic mycorrhizal fungi. Preferential hyphal colonization of the calcium silicate-bearing rock, basalt, progressively increased with advancement from arbuscular mycorrhizal (AM) to later, independently evolved ectomycorrhizal (EM) fungi, and from gymnosperm to angiosperm hosts with both fungal groups. This led to ‘trenching’ of silicate mineral surfaces by AM and EM fungi, with EM gymnosperms and angiosperms releasing calcium from basalt at twice the rate of AM gymnosperms. Our findings indicate mycorrhiza-driven weathering may have originated hundreds of millions of years earlier than previously recognized and subsequently intensified with the evolution of trees and mycorrhizas to affect the Earth's long-term CO2 and climate history.

The mechanism of green rust sulfate (GR-SO(4)) formation was determined using a novel in situ approach combining time-resolved synchrotron-based wide-angle X-ray scattering (WAXS) with highly controlled chemical synthesis and electrochemical (i.e., Eh and pH) monitoring of the reaction. Using this approach,GR-SO(4) was synthesized under strictly anaerobic conditions by coprecipitation from solutions with known Fe(II)/Fe(III) ratios (i.e., 1.28 and 2) via the controlled increase of pH. The reaction in both systems proceeded via a three-stage precipitation and transformation reaction. During the first stage,schwertmannite (Fe(8)O(8)(OH)(4.5)(SO(4))(1.75)) precipitated directly from solution at pH 2.8-4.5. With increasing pH (>5), Fe(2+) ions adsorb to the surface of schwertmannite and catalyze its transformation to goethite (alpha-FeOOH) during the second stage of the reaction. In the third stage, the hydrolysis of the adsorbed Fe(2+) ions on goethite initiates its transformation to GR-SO(4) at pH >7. The GR-SO(4) then continues to crystallize up to pH approximately 8.5. These results suggest that with an Fe(II)/Fe(III) ratio of < or = 2 in the initial solution the structural Fe(II)/Fe(III) of the GR-SO(4) will be close to that of the starting composition.

Macromolecular binding to minerals is of great importance in the formation of biofilms, and carboxylate functional groups have been found to play a pivotal role in the functioning of these macromolecules. Here we present both fluorescence time-resolved anisotropy measurements and simulation data on the conformational behaviour and binding of a poly acrylic acid polymer. In solution the polymer exhibits a pH dependent behaviour, with a coiled conformation at a low pH and extended conformation at higher pH values. The polymer is readily adsorbed on the surface of calcite, preferring to bind in an extended conformation, with the strength of the adsorption dependent on the pH and presence of counter ions. We discuss the reasons why the calculated adsorption free energy differs from that obtained from a Langmuir isotherm analysis, showing that they refer to different quantities. The enhanced binding of the extended conformations shows the importance of flexibility in the binding of macromolecules.

Direct-placement dental restorative materials include dental amalgam, glass ionomer, resin-modified glass ionomer, compomer and resin-based composite (RBC). The choice of restorative material is determined by its ability to restore the structure and/or the aesthetic appearance of the dentition and to impart a net therapeutic value. In this way, the most appropriate material system is chosen to manage each particular clinical situation in the most effective manner. The most commonly used direct-placement materials in everyday modern dentistry are dental amalgam and resin-based composites. To date, concerns about the environmental impact from the use of dental materials has focused on dental amalgam and mercury release. It is now evident that the continued use of dental amalgam is time-limited on the basis of environmental pollution as recommended by the Minamata Treaty. The recommendations include a planned phase-down of use of dental amalgam with an anticipated complete phase-out by 2030. The environmental impact of other restorative dental materials deserves further consideration. This article provides a detailed overview of the environmental issues associated with the use of dental amalgam, the potential environmental issues associated with the alternative resin-based composite restorative materials and to consider recommendations for further research.

Farm-level sustainable intensification of agriculture (SIA) has become an important concept to ensuring food security while minimising negative externalities. However, progress towards its achievement is often constrained by the different perceptions and goals of various stakeholders that affect farm management decisions. This study examines farm-level SIA as a dynamic system with interactive components that are determined by the interests of the stakeholders involved. A systems thinking approach was used to identify and describe the pathways towards farm-level SIA across the three main pillars of sustainability. An explanatory network analysis of fuzzy cognitive maps (FCMs) that were collectively created by representative groups of farmers, farm advisors and policy makers was performed. The study shows that SIA is a complex dynamic system, affected by cognitive beliefs and particular knowledge within stakeholder groups. The study concludes that, although farm-level SIA is a complex process, common goals can be identified in collective decision making.

Clinical applications of resin-based composite (RBC) generate environmental pollution in the form of microparticulate waste. Methods: SEM, particle size and specific surface area analysis, FT-IR and potentiometric titrations were used to characterise microparticles arising from grinding commercial and control RBCs as a function of time, at time of generation and after 12 months ageing in water. The RBCs were tested in two states: (i) direct-placement materials polymerised to simulate routine clinical use and (ii) pre-polymerised CAD/CAM ingots milled using CAD/CAM technology. Results: The maximum specific surface area of the direct-placement commercial RBC was seen after 360 s of agitation and was 1290 m2/kg compared with 1017 m2/kg for the control material. The median diameter of the direct-placement commercial RBC was 6.39 μm at 360 s agitation and 9.55 μm for the control material. FTIR analysis confirmed that microparticles were sufficiently unique to be identified after 12 months ageing and consistent alteration of the outermost surfaces of particles was observed. Protonation-deprotonation behaviour and the pH of zero proton charge (pHzpc) ≈ 5–6 indicated that the particles are negatively charged at neutral pH7. Conclusion: The large surface area of RBC microparticles allows elution of constituent monomers with potential environmental impacts. Characterisation of this waste is key to understanding potential mitigation strategies.

As resin-based composites (RBC) replace dental amalgam for environmental reasons, there is a requirement to understand the environmental impact of this alternative dental restorative material. In this study we standardize the simultaneous detection of five monomeric components associated with RBCs using high performance liquid chromatography (HPLC) coupled with solid-phase microextraction (SPME). Factors affecting method performance (detection wavelength, calibration conditions, method sensitivity/ accuracy/precision, extraction time/efficiency) are evaluated using standard solutions containing the mixture of TEGDMA, UDMA, Bis-GMA, BPA and HEMA. Detection sensitivity and analytical efficiency of the method is optimized for these compounds using 200 nm detection wavelength, PDMS/DVB fiber and extraction time of 90 min. Analytical accuracy of the HPLC is >95% for all monomers, with precision of 2.3-5.1%. Detection limits under the conditions described are 25 µg/L for HEMA, BPA, UDMA, Bis-GMA, and 100 µg/L for TEGDMA. The extraction time is governed by the largest molecular weight compounds.

Sustainable intensification of agriculture (SIA) has become an important concept to ensuring food security in the context of increasing agricultural production while minimising negative externalities in contemporary agronomic systems. In supporting this, there is a need to establish a decision-making and management system that involves the views and opinions of different stakeholders and unifies the goals of SIA amongst them. The objective of this work is to identify and describe pathways toward farm-level SIA. An explanatory network approach and fuzzy cognitive maps (FCMs) support the analysis of stakeholder views across the three pillars of sustainability: social, economic and environmental. Different stakeholder groups were asked to collectively map the pathways towards farm level SIA in a workshop exercise. The respective groups considered a common set of pre-selected factors as potential descriptors of sustainability and created unique maps by adding their own components and descriptors and identifying causal links between them. While the relative weighting of factors by each group differed, according to their perspectives and interpretation, yield, knowledge transfer, water quality, weather extremes and technology/infrastructure were scored as priority descriptors of farm-level sustainability by all groups in an aggregate analysis. Exploratory analysis of FCMs was found to provide an efficient mechanism to investigate stakeholder views on pathways towards farm-level SIA, by identifying causal relationships and interactions between factors and actors that affect its achievement. The study shows that sustainable intensification is a complex dynamic system that includes institutional structures, personal goals, stakeholder interests and socio-economic factors, and is affected by cognitive beliefs and particular knowledge within stakeholder groups. Our results show how experience, knowledge and beliefs affect the perception of farm-level SIA by various stakeholder groups, and how this knowledge is often fragmented and miscommunicated. The exercise confirmed the hypothesis that farm-level SIA has to be seen as a dynamic process in which farm performance is affected by various factors, with the complexity of the process increasing when different stakeholder interests and beliefs combine for farm management.