The economic significance of the phytoextraction of nickel, cobalt and gold from metalliferous soils : a thesis in partial fulfilment of the requirements for the degree of Master of Science at Massey University

Phytoextraction of heavy metals is a relatively new technology that has potential applications for the remediation of many contaminated sites around the world. The technology has significant applications in the minerals industry for the treatment of low-grade ores and metalliferous mine waste. This study concerns the investigation of the potential to remove heavy metals, in particular nickel, cobalt and gold, from artificial and lateritic substrates. Four experiments comprise this study of the phytoextraction of nickel, cobalt and gold using both accumulator and non-accumulator species. Nickel and cobalt bioavailability was determined by ammonium acetate extraction for both artificial and laterite substrates. It was found that ammonium acetate extractability was predictive for nickel accumulation from a nickel-only artificial substrate. Cobalt bioavailability did not predict the accumulation response of either Alyssum bertolonii or Berkheya coddii grown of artificial substrates. The potential for phytoextraction of nickel and cobalt was investigated using the known nickel hyperaccumulators A. bertolonii and B. coddii, grown on artificially prepared substrates. The substrates were nickel-only (4 mg/kg to 1000 mg/kg), cobalt-only (4 mg/kg to 1000 mg/kg) and nickel-cobalt mixed (1:1 ratio, 4 mg/kg to 500 mg/kg) amendments of sulphates to commercial potting mix. Hyperaccumulation from nickel-only and cobalt-only substrates resulted in typical logarithmic metal uptake by both species. The cobalt-only substrates were phytotoxic to B. coddii above a concentration of 15-20 mg/kg. Phytotoxicity significantly reduced biomass production in B. coddii without effecting the bioaccumulation coefficient. No corresponding cobalt phytotoxicity was observed in A. bertolonii over the experimental range, although biomass production appears to favour substrate concentrations below 30 mg/kg. The bioavailability and hyperaccumulation of cobalt from the mixed nickel-cobalt substrates dramatically reduced the nickel accumulation potential of both species at substrate concentrations below 300 mg/kg. At higher substrate metal concentrations both species return to nickel dominant hyperaccumulation. Induced gold accumulation in B. coddii and Iberis intermedia was investigated using, sequential ammonium thiocyanate and ammonium thiosulphate chelation to, a 5 mg/kg gold artificial substrate. An attempt to determine gold bioavailability by ammonium thiocyanate and ammonium thiosulphate extraction was made on the substrate. It was found that neither chelator extraction could be correlated with plant accumulation induced by the same concentration of the reagent. Ammonium thiocyanate induction resulted in plant gold accumulation at or below the substrate concentration. Ammonium thiosulphate induced gold accumulation in I. Intermedia reached 48.8 mg/kg when treatment with a 1% solution. B. coddii accumulated 9.3 mg/kg gold for the same treatment. Five consignments of metalliferous lateritic materials from Western Australia were investigated. Three substrates originated from Project Murrin Murrin nickel and cobalt mine operated by Anaconda Nickel Ltd. and two substrates originated from Boddington Gold Mine operated by Worsley Alumina Ltd. Nickel and cobalt accumulation by A. bertolonii and B. coddii was found to be significantly lower than observed using artificial substrates. Nickel and cobalt bioavailability, determined by ammonium acetate extraction, failed to predict the accumulation responses from laterite substrates. This is attributed to elemental interference by, and possibly ammonium acetate chelation of, other mobile heavy metals in these substrates. A hypothesis deserved of further research. Hyperaccumulation of nickel was observed for both species on the Anaconda Nickel Ltd. SAP substrate only. Appreciable cobalt accumulation (≈90 mg/kg) was observed on the SAP substrate for both species and on the Boddington Gold Mine B5 substrate for B. coddii. Phytomining scenarios were determined for both species grown on the SAP substrate. A. bertolonii could produce 13 kg of nickel and 0.8 kg of cobalt per hectare with a value of US$163. B. coddii could produce 23.8 kg of nickel and 2.1 kg of cobalt per hectare at a value of US$ 319. These levels of production could be improved by fertilisation and/or substrate acidification. A preliminary investigation into induced gold accumulation from laterite substrates by I. Intermedia, A. longiflora, Brassica juncea and Limum usitatissimum was made using the acid biased chelator ammonium thiocyanate. It was found that an acidified amendment of ammonium thiocyanate greatly improved the phytoaccumulation of gold from the lateritic substrates. An amendment of 2M HC1 produced appreciable gold mobility and phytoaccumulation and indicates that gold solubility is the primary control on plant uptake. Analysis of various plant tissues indicated that Acacia longiflora stored significant gold in its roots compared to foliar components. All plant-substrate combinations indicated a trend towards increasing acidification and gold phytoaccumulation. No plant-substrate-treatment combination produced an economically viable phytomining scenario

Later life in rental housing

Historically, New Zealand has had relatively high rates of home ownership, with widely held aspirations for mortgage-free tenure in later life. As a consequence, examination of the small but growing numbers of older renters has been limited. This article draws together local research, commissioned policy development work and comparative evidence to identify the characteristics of older people in rental accommodation, current and projected issues and potential policy issues

Building machines that learn and think about morality

Lake et al. propose three criteria which, they argue, will bring artificial intelligence (AI) systems closer to human cognitive abilities. In this paper, we explore the application of these criteria to a particular domain of human cognition: our capacity for moral reasoning. In doing so, we explore a set of considerations relevant to the development of AI moral decision-making. Our main focus is on the relation between dual-process accounts of moral reasoning and model-free/model-based forms of machine learning. We also discuss how work in embodied and situated cognition could provide a valu- able perspective on future research

WKB approach and quantum corrections to classical dynamics in the Josephson problem

We apply a many-body Wentzel-Kramers-Brillouin (WKB) approach to determine the leading quantum corrections to the semiclassical dynamics of the Josephson model, describing interacting bosons able to tunnel between two localized states. The semiclassical dynamics is known to divide between regular oscillations and self-trapped oscillations where the sign of the imbalance remains fixed. In both cases, the WKB wave functions are matched to Airy functions, yielding a modified Bohr-Sommerfeld quantization condition. At the critical energy dividing normal and self-trapped oscillations, the WKB wave functions should instead be matched to parabolic cylinder functions, leading to a quantization formula that is not just the Bohr-Sommerfeld formula, and recovering the known logarithmic quantum break times at this energy. This work thus provides another illustration of the usefulness of the WKB approach in certain many-body problems.Comment: references updated, introduction re-writte

Spatial dynamics, thermalization, and gain clamping in a photon condensate

We study theoretically the effects of pump-spot size and location on photon condensates. By exploring the inhomogeneous molecular excitation fraction, we make clear the relation between spatial equilibration, gain clamping and thermalization in a photon condensate. This provides a simple understanding of several recent experimental results. We find that as thermalization breaks down, gain clamping is imperfect, leading to "transverse spatial hole burning" and multimode condensation. This opens the possibility of engineering the gain profile to control the condensate structure.Comment: Further extended, including new figures. Now 10 figure

On Lipschitz continuity of nonlinear differential operators

In connection with approximations for nonlinear evolution equations, it is standard to assume that nonlinear terms are at least locally Lipschitz continuous. However, it is shown here that f = f(X,del sub u(X)) is Lipschitz continuous from the subspace W sup 1, infinity is a subset of L sub 2 into W sup 1,2, and maps W sup 2, infinity into W sup 1, infinity, if and only if f is affine with W sup 1, infinity coefficients. In fact, a local version of this claim is proved

Galerkin/Runge-Kutta discretizations for parabolic equations with time dependent coefficients

A new class of fully discrete Galerkin/Runge-Kutta methods is constructed and analyzed for linear parabolic initial boundary value problems with time dependent coefficients. Unlike any classical counterpart, this class offers arbitrarily high order convergence while significantly avoiding what has been called order reduction. In support of this claim, error estimates are proved, and computational results are presented. Additionally, since the time stepping equations involve coefficient matrices changing at each time step, a preconditioned iterative technique is used to solve the linear systems only approximately. Nevertheless, the resulting algorithm is shown to preserve the original convergence rate while using only the order of work required by the base scheme applied to a linear parabolic problem with time independent coefficients. Furthermore, it is noted that special Runge-Kutta methods allow computations to be performed in parallel so that the final execution time can be reduced to that of a low order method

Galerkin/Runge-Kutta discretizations for semilinear parabolic equations

A new class of fully discrete Galerkin/Runge-Kutta methods is constructed and analyzed for semilinear parabolic initial boundary value problems. Unlike any classical counterpart, this class offers arbitrarily high, optimal order convergence. In support of this claim, error estimates are proved, and computational results are presented. Furthermore, it is noted that special Runge-Kutta methods allow computations to be performed in parallel so that the final execution time can be reduced to that of a low order method

Lie algebra solution of population models based on time-inhomogeneous Markov chains

Many natural populations are well modelled through time-inhomogeneous stochastic processes. Such processes have been analysed in the physical sciences using a method based on Lie algebras, but this methodology is not widely used for models with ecological, medical and social applications. This paper presents the Lie algebraic method, and applies it to three biologically well motivated examples. The result of this is a solution form that is often highly computationally advantageous.Comment: 10 pages; 1 figure; 2 tables. To appear in Applied Probabilit

Targeting vaccination against novel infections : risk, age and spatial structure for pandemic influenza in Great Britain

The emergence of a novel strain of H1N1 influenza virus in Mexico in 2009, and its subsequent worldwide spread, has focused attention to the question of optimal deployment of mass vaccination campaigns. Here, we use three relatively simple models to address three issues of primary concern in the targeting of any vaccine. The advantages of such simple models are that the underlying assumptions and effects of individual parameters are relatively clear, and the impact of uncertainty in the parametrization can be readily assessed in the early stages of an outbreak. In particular, we examine whether targeting risk-groups, age-groups or spatial regions could be optimal in terms of reducing the predicted number of cases or severe effects; and how these targeted strategies vary as the epidemic progresses. We examine the conditions under which it is optimal to initially target vaccination towards those individuals within the population who are most at risk of severe effects of infection. Using age-structured mixing matrices, we show that targeting vaccination towards the more epidemiologically important age groups (5-14 year olds and then 15-24 year olds) leads to the greatest reduction in the epidemic growth and hence reduces the total number of cases. Finally, we consider how spatially targeting the vaccine towards regions of country worst affected could provide an advantage. We discuss how all three of these priorities change as both the speed at which vaccination can be deployed and the start of the vaccination programme is varied