The great metals boom: A retrospective

The metals boom that ran from 2003 to 2008 represented the most powerful and sustained such boom since the Second World War. As the boom gathered momentum, the notion began to emerge that commodities were at the beginning of a multi-year ‘super cycle’ driven by demand growth in the emerging economies and, in particular, China. The persistence of the boom helped sustain this belief right up to the point when metal prices collapsed in the second half of 2008. Looking back over the period, much of what occurred can be readily explained by the unusual strength of the demand shock and the lagged response of the supplying industry, with prices receiving an additional boost from the activities of commodity investors. There is, however, some evidence to suggest that the combination of downward pressure on the costs of manufactured goods and upward pressure on the costs of mineral commodities which accompanied the boom marked a shift in the terms of trade between these two product groups. This in turn seems to have brought to an end the sustained decline in real terms metal prices that occurred in the years following the boom of the 1970s. In sum, the key structural change taking place may not have been on the demand side of the industry as the super cyclists maintained, but on the supply side.     

Uncertainty and sensitivity analysis of spatial predictions of heavy metals in wheat

Heavy metals seriously threaten the health of human beings when they enter the food chain. Therefore, policymakers require precise predictions of heavy metal concentrations in agricultural crops. In this paper we quantify the uncertainty of regression predictions of Cd and Pb in wheat (Triticum aestivum L.) and the contributions to the uncertainties in these predictions associated with inputs to the regression model. For each node of the 500- x 500-m grid covering the arable soils in The Netherlands, a latin hypercube sample size of 1000 is constructed from the uncertainty distributions of the explanatory variables (pH, soil organic matter [SOM], and heavy metal concentration in soil), the regression coefficients, and the random term of the regression model. This sample is used as input for the regression model to obtain 1000 values from the uncertainty distributions of the log(Cd) and log(Pb) concentration in wheat. There were no nodes where the recent EU quality standards for Cd and Pb (0.2 mg kg(-1) fresh wt.) in wheat were almost certain to be exceeded. For most nodes with clay soils, the quality standard for Cd in wheat almost certainly will not be exceeded; for Pb this is much less certain. The uncertainty in the Cd concentration in soil contributes most to the uncertainty in the predicted Cd concentrations in wheat (36% on the average), followed by the random term of the regression model (23%). For Pb the contribution of the random term is by far the largest (52%).     

Environmental risks of applying sewage sludge compost to vineyards: carbon,heavy metals,nitrogen, and phosphorus accumulation

Biosolids are applied to vineyards to supply organic matter. However, there is concern that this practice can increase the concentration of macronutrients and heavy metals in the soil, some of which can leach. We evaluated the environmental hazard of sewage sludge compost applied in March 1999 at 10, 30, and 90 Mg ha-1 fresh weight in a vineyard in southeastern France. Soil organic matter increased in all plots by 3 g kg-1 18 mo after the amendment. Neither total nor available heavy metal concentrations increased in the soil. Mineral nitrogen (N) in the topsoil of amended plots of 10, 30, and 90 Mg ha-1 increased by 5, 14, and 26 kg (NO3(-)-N + NH4(+)-N) ha-1, respectively, the first summer and by 2, 5, and 10 kg (NO3(-)-N + NH4(+)-N) ha-1, respectively, the second summer compared with controls. At the recommended rate, risks of N leaching is very low, but phosphorus (P) appeared to be the limiting factor. Phosphorus significantly increased only in plots amended with the highest rate in the topsoil and subsoil. At lower rates, although no significant differences were observed, P added was greater than the quantities absorbed by vines. In the long run, P will accumulate in the soil and may reach concentrations that will pose a risk to surface waters and ground water. Therefore, although the current recommended rate (10 Mg ha-1) increased soil organic matter without the risk of N leaching, total sewage sludge loading rates on vineyards should be based on P concentrations.     

Soil and litter phosphorus-31 nuclear magnetic resonance spectroscopy: extractants, metals, and phosphorus relaxation times

Phosphorus-31 nuclear magnetic resonance (NMR) spectroscopy is an excellent tool with which to study soil organic P, allowing quantitative, comparative analysis of P forms. However, for 31P NMR to be tative, all peaks must be completely visible, and in their correct relative proportions. There must be no line broadening, and adequate delay times must be used to avoid saturation of peaks. The objective of this study was to examine the effects of extractants on delay times and peak saturation. Two samples (a forest litter and a mineral soil sample) and three extractants (0.25 M NaOH, NaOH plus Chelex (Bio-Rad Laboratories, Hercules, CA), and NaOH plus EDTA) were used to determine the differences in the concentration of P and cations solubilized by each extractant, and to measure spin-lattice (T1) relaxation times of P peaks in each extract. For both soil and litter, NaOH-Chelex extracted the lowest concentrations of P. For the litter sample, T1 values were short for all extractants due to the high Fe concentration remaining after extraction. For the soil sample, there were noticeable differences among the extractants. The NaOH-Chelex sample had less Fe and Mn remaining in solution after extraction than the other extractants, and the longest delay times used in the study, 6.4 s, were not long enough for quantitative analysis. Delay times of 1.5 to 2 s for the NaOH and NaOH-EDTA were adequate. Line broadening was highest in the NaOH extracts, which had the highest concentration of Fe. On the basis of these results, recommendations for future analyses of soil and litter samples by solution 31P NMR spectroscopy include: careful selection of an extractant; measurement of paramagnetic ions extracted with P; use of appropriate delay times and the minimum number of scans; and measurement of T1 values whenever possible.     

Trace metals in river bed sediments: An assessment of their partitioning and bioavailability by using multivariate exploratory analysis

In this study, river bed sediments were submitted to a BCR sequential extraction, together with three bioavailability tests: a weak acid elutriate (HCl), a physiologically based extraction test (PBET) and a toxicity characteristic leaching procedure (TCLP). The most remarkable features of the BCR procedure were: i) Mn and Zn showed the highest proportion of the F1 exchangeable fraction; ii) in addition to Fe, Pb and Zn were the metals with the higher percentages in the F2 reducible fraction; iii) Fe and Cu were the elements with the highest proportion of the F3 oxidizable fraction; iv) the application of Principal Component Analysis to the metals in each of the three fractions did not show clear associations between metals and sediment components considered as metal scavengers, v) considering the sum of the three BCR fractions, the elements showed a decreasing availability of: Fe > Pb > Zn > Cu > Mn > Ni > Cr. The single extractions followed a decreasing extractability order of: HCl > PBET > TCLP and they were far from the extractability deduced from the sum of fractions in the BCR extraction.     

Understanding world metals prices—Returns,volatility and diversification

In recent times, the prices of internationally traded metals have reached record highs and there is considerable uncertainty regarding their future. This phenomenon is partially driven by strong demand from a small number of emerging economies, such as China and India. This paper uses a long time-series (1900–2007) on 21 metals prices to investigate their properties, and presents unique features of their volatility, including a decomposition into within- and between-group components. If most volatility is commodity-specific rather than “global”, then metals-exporting dependent economies can smooth income via diversification.     

Speciation of some heavy metals in River Nile sediments,Cairo, Egypt

River sediments are basic components of our environment. It also constitutes a major source of persistent bioaccumulative toxic chemicals which may pose threats to ecological and human health even after contaminants are no longer released from point and non-point sources. Therefore, the aim of this study was to investigate the mobility and the availability of metals in sediments from different sites along the Nile River in Cairo district using sequential chemical extraction technique. The speciation data showed that most metals were associated with organic/sulfide and residual fractions. The order of total metal concentrations in sediment samples was found to be Fe > Mn > Zn > Ni > Cu ≥ Cr > Pb > Cd.     

The USSR, China, India and the world metals industry to 2010

Remarkable changes are occurring within the economies of the USSR, China and India that are influencing mineral industry activities. These three countries account for a major share of world minerals production and consumption. Their domestic reforms may ultimately have a serious impact on the global mining industry. This paper examines the present status of the Soviet, Chinese and Indian mineral industries, and forecasts conditions to 2010. Long-term characteristics analysed include industrial production, intensity of use, consumption, mine and plant expansion and trade policy. Six metals are highlighted in the study – aluminium, copper, lead, nickel, steel and zinc.     

Economic rent : Incidence in selected metals and minerals

The magnitude of the ‘economic rent’ and its distribution among producing countries, mineral exploitation companies and consumers has become a dominant issue in national and international policy formulation, but the difficulties in measuring the rent add to the problems of determining its equitable distribution. This paper examines the nature of the rent and estimates its incidence in bauxite, copper, iron ore, phosphate rock, tin and petroleum. Rents were found to be low for bauxite and iron ore. Bauxite, phosphates and petroleum producers have increased their share of the rent, though this trend now seems to be reversing for bauxite and phosphates. Only in tin, and to a lesser extent petroleum, have the exporting countries captured significant shares in total rent. Otherwise, the rent is largely concentrated at the processing stage, which suggests that processing plant would have to shift to the producing countries if they are to claim a larger share.     

Enhancing phytoextraction: the effect of chemical soil manipulation on mobility, plant accumulation, and leaching of heavy metals

For heavy metal-contaminated agricultural land, low-cost, plant-based phytoextraction measures can be a key element for a new land management strategy. When agents are applied into the soil, the solubility of heavy metals and their subsequent accumulation by plants can be increased, and, therefore, phytoextraction enhanced. An overview is given of the state of the art of enhancing heavy metal solubility in soils, increasing the heavy metal accumulation of several high-biomass-yielding and metal-tolerant plants, and the effect of these measures on the risk of heavy metal leaching. Several organic as well as inorganic agents can effectively and specifically increase solubility and, therefore, accumulation of heavy metals by several plant species. Crops like willow (Salix viminalis L.), Indian mustard [Brassica juncea (L.) Czern.], corn (Zea mays L.), and sunflower (Helianthus annuus L.) show high tolerance to heavy metals and are, therefore, to a certain extent able to use the surpluses that originate from soil manipulation. More than 100-fold increases of lead concentrations in the biomass of crops were reported, when ethylenediaminetetraacetic acid (EDTA) was applied to contaminated soils. Uranium concentrations could be strongly increased when citric acid was applied. Cadmium and zinc concentrations could be enhanced by inorganic agents like elemental sulfur or ammonium sulfate. However, leaching of heavy metals due to increased mobility in soils cannot be excluded. Thus, implementation on the field scale must consider measures to minimize leaching. So, the application of more than 1 g EDTA kg(-1) becomes inefficient as lead concentration in crops is not enhanced and leaching rate increases. Moreover, for large-scale applications, agricultural measures as placement of agents, dosage splitting, the kind and amount of agents applied, and the soil properties are important factors governing plant growth, heavy metal concentrations, and leaching rates. Effective prevention of leaching, breeding of new plant material, and use of the contaminated biomass (e.g., as biofuels) will be crucial for the acceptance and the economic breakthrough of enhanced phytoextraction.     

Herbaceous vegetation productivity, persistence, and metals uptake on a biosolids-amended mine soil

The selection of plant species is critical for the successful establishment and long-term maintenance of vegetation on reclaimed surface mined soils. A study was conducted to assess the capability of 16 forage grass and legume species in monocultures and mixes to establish and thrive on a reclaimed Appalachian surface mine amended with biosolids. The 0.15-ha coarse-textured, rocky, non-acid forming mined site was prepared for planting by grading to a 2% slope and amending sandstone overburden materials with a mixture of composted and dewatered, anaerobically digested biosolids at a rate of 368 Mg ha(-1) (dry weight). Tall fescue (Festuca arundinacea Schreb.), orchardgrass (Dactylis glomerata L.), switchgrass (Panicum virgatum L.), caucasian bluestem (Bothriochloa caucasia L.), reed canarygrass (Phalaris arundinacea L.), ladino clover (Trifolium repens L.), birdsfoot trefoil (Lotus corniculatus L.), crownvetch (Coronilla varia L.), alfalfa (Medicago sativa L.), common sericea lespedeza and AULotan sericea lespedeza (Lespedeza cuneata L.), tall fescue-ladino clover, tall fescue-alfalfa, orchardgrass-birdsfoot trefoil, switchgrass-AULotan, and an herbaceous species mix intended for planting on reforested sites consisting of foxtail millet [Setaria italica (L.) Beauv.], perennial ryegrass (Lolium perenne L.), redtop (Agrostis alba L.), kobe lespedeza (Kummerowia striata L.), appalow lespedeza (Lespedeza cuneata L.), and birdsfoot trefoil were established between spring 1990 and 1991. Vegetative biomass and/or persistence were assessed in 1996, 1997, 1998, 2000, 2001, and 2002. The high rate of biosolids applied provided favorable soil chemical properties but could not overcome physical property limitations due to shallow undeveloped soil perched atop a compacted soil layer at 25 cm depth. The plant species whose persistence and biomass production were the greatest after a decade or more of establishment (i.e., switchgrass, sericea lespedeza, reed canarygrass, tall fescue, and crownvetch) shared the physiological and reproductive characteristics of low fertility requirements, drought and moisture tolerance, and propagation by rhizome and/or stolons. Of these five species, two (tall fescue and sericea lespedeza) are or have been seeded commonly on Appalachian coal surface mines, and often dominate abandoned pasture sites. Despite the high rates of heavy metal-bearing biosolids applied to the soil, plant uptake of Cd, Cu, Ni, and Zn were well within critical concentrations more than a decade after establishment of the vegetation.     

Bioleaching of heavy metals from sewage sludge: A review

During the treatment of sewage, a huge volume of sludge is generated, which is disposed of on land as soil fertilizer/conditioner due to the presence of nitrogen, phosphorus, potassium and other nutrients. However, the presence of toxic heavy metals and other toxic compounds in the sludge restricts its use as a fertilizer. Over the years, bioleaching has been developed as an environmentally friendly and cost-effective technology for the removal of heavy metals from the sludge. The present paper gives an overview of the various bioleaching studies carried out in different modes of operation. The various important aspects such as pathogen destruction, odor reduction and metal recovery from acidic leachate also have been discussed. Further, a detailed discussion was made on the various technical problems associated with the bioleaching process, which need to be addressed while developing the process on a larger scale.     

Phytoextraction of toxic metals: a review of biological mechanisms

Remediation of sites contaminated with toxic metals is particularly challenging. Unlike organic compounds, metals cannot be degraded, and the cleanup usually requires their removal. However, this energy-intensive approach can be prohibitively expensive. In addition, the metal removing process often employs stringent physicochemical agents which can dramatically inhibit soil fertility with subsequent negative impacts on the ecosystem. Phytoremediation has been proposed as a cost-effective, environmental-friendly alternative technology. A great deal of research indicates that plants have the genetic potential to remove many toxic metals from the soil. Despite this potential, phytoremediation is yet to become a commercially available technology. Progress in the field is hindered by a lack of understanding of complex interactions in the rhizosphere and plant-based mechanisms which allow metal translocation and accumulation in plants. In this paper, four research areas relevant to metal phytoextraction from contaminated soil are reviewed. The review concludes with an assessment of the current status of technology deployment and suggestions for future phytoremediation research.     

Theory of storage,inventory and volatility in the LME base metals

The theory of storage, as related to commodities, makes two predictions involving the quantity of the commodity held in inventory. When inventory is low (i.e. a situation of scarcity), spot prices will exceed futures prices, and spot price volatility will exceed futures price volatility. Conversely, during periods of no scarcity, both spot prices and spot price volatility will remain relatively subdued. We test these predictions for the six base metals traded on the London Metal Exchange (aluminium, copper, lead, nickel, tin and zinc), and find strong validation for the theory. Including Chinese inventories reported by the Shanghai Futures Exchange strengthens the relationship further. We also introduce the concepts of excess volatility, inventory-implied spot price and inventory-implied spot volatility and illustrate some applications.     

Dynamic metals demand model

Studies by Nutting, Jacobson and Evans and Georgentalis et al. have all concluded, using panel data sets, that a number of metals appear to share a common demand curve that is stable over time. However, these studies have a number of theoretical and econometric limitations. This paper addresses these concerns and reassesses the hypothesis that some metals share such a common demand curve with the same price elasticity of demand. This is achieved within the framework of a random coefficients model. This model was applied to a dynamic metals demand function (DLR) and various estimation techniques were used including OLS, IV, Empirical Bayes (EB) and Instrumental Variables Empirical Bayes (IV-EB). It was found that each metal had its own individual short run demand function with statistically different own price and industrial activity elasticities of demand. In the long run, each metal appeared to be equally unresponsive to price changes, but had different industrial activity elasticities. The speeds of price adjustment to periods of market disequilibrium differed substantially between metals.     

Assessing potential bioavailability of metals in sediments: A proposed approach

Due to anthropogenic inputs, elevated concentrations of metals frequently occur in aquatic sediments. In order to make defensible estimates of the potential risk of metals in sediments and/or develop sediment quality criteria for metals, it is essential to identify that fraction of the total metal in the sediments that is bioavailable. Studies with a variety of benthic invertebrates indicate that interstitial (pore) water concentrations of metals correspond very well with the bioavailability of metals in test sediments. Many factors may influence pore water concentrations of metals; however, in anaerobic sediments a key phase controlling partitioning of several cationic metals (cadmium, nickel, lead, zinc, copper) into pore water is acid volatile sulfide (AVS). In this paper, we present an overview of the technical basis for predicting bioavailability of cationic metals to benthic organisms based on pore water metal concentrations and metal-AVS relationships. Included are discussions of the advantages and limitations of metal bioavailability predictions based on these parameters, relative both to site-specific assessments and the development of sediment quality criteria.