Looking forward through the past: identification of 50 priority research questions in palaeoecology

1. Priority question exercises are becoming an increasingly common tool to frame future agendas in conservation and ecological science. They are an effective way to identify research foci that advance the field and that also have high policy and conservation relevance. 2. To date, there has been no coherent synthesis of key questions and priority research areas for palaeoecology, which combines biological, geochemical and molecular techniques in order to reconstruct past ecological and environmental systems on time-scales from decades to millions of years. 3. We adapted a well-established methodology to identify 50 priority research questions in palaeoecology. Using a set of criteria designed to identify realistic and achievable research goals, we selected questions from a pool submitted by the international palaeoecology research community and relevant policy practitioners. 4. The integration of online participation, both before and during the workshop, increased international engagement in question selection. 5. The questions selected are structured around six themes: human–environment interactions in the Anthropocene; biodiversity, conservation and novel ecosystems; biodiversity over long time-scales; ecosystem processes and biogeochemical cycling; comparing, combining and synthesizing information from multiple records; and new developments in palaeoecology. 6. Future opportunities in palaeoecology are related to improved incorporation of uncertainty into reconstructions, an enhanced understanding of ecological and evolutionary dynamics and processes and the continued application of long-term data for better-informed landscape management

Ammonium phosphate slurry rheology and particle properties - The influence of Fe(III) and A(III) impurities, solid concentration and degree of neutralization

Ammonium phosphate slurries are produced from impure phosphoric acid that contains Fe(III), Al(III) and Mg(II) ions. The insolubility of these metal ions and the onset of solid formation determined as a function of pH or mole ratio (MR) of ammonia to phosphoric acid were consistent with the trend for the pH of formation of the first hydrolysis product that decreases in the following order: Fe(III)<Al(III)<Mg(II). The hydrolysis products of Fe(III) formed at pH>2.0 or MR>0.5 initiate ammonium phosphate crystallization, reduce the size of particles formed and generate attractive interparticle forces. Similarly, the Al(III) hydrolysis products formed later at pH>2.6 MR>0.7), will also initiate further crystallization, adsorb on particles and produce attractive forces. The attractive forces and the high number concentration of particle—particle interactions are responsible for the increased viscosity and non-Newtonian flow behavior displayed at increasing Fe(III) and Al(III) concentration. Mg(II) ions are not hydrolyzed at MR<1.0 so its effect on rheology is negligible and its effect at MR<1.0 is also small as its concentration is much smaller than that of Fe(III) and Al(III) ions. The change in slurry viscosity with the degree of neutralization is also explained in terms of particle size distribution, solubility and solids concentration variations

Entrainment of a two-layer liquid through a taphole

Entrainment through a taphole of a two-layer system has been investigated. The results showed that for liquids with low viscosities, the minimum dimensionless clearance from the taphole before entrainment occurs can be predicted theoretically and was related to the Froude number as Fr0.4. At low Froude numbers less than 1, fluids with low viscosities resulted in the entrainment showing a positive deviation from the critical Froude number. This allowed tapping to be carried out without entrainment occurring, even when the liquid-liquid interface was within the region of the taphole diameter. For liquids with appreciable viscosities, the entrainment showed a negative deviation from the critical Froude number. This occurs for the tapping of slag and results in entrainment at a higher liquid-liquid interface height than is predicted theoretically. Entrainment was more likely to happen for slag tapping than for matte tapping. A ledge below the taphole was found to reduce entrainment, enabling the liquid-liquid interface to be closer to the taphole during tapping. This resulted in improved slag removal efficiencies and reduced matte or metal entrainment, coupled with less slag left in the furnace after tapping. The length of the ledge from the taphole into the slag was found to be the controlling parameter for entrainment, while the ledge thickness had no effect on entrainment