Graeme Spiers

TRACE ELEMENT CONTENT OF SELECTED FERTILIZERS AND DAIRY MANURES AS DETERMINED BY ICP–MS

The trace element composition of representative fertilizers, liming agents, and dairy manures applied on farms in New York was measured because there has been recent concern about toxic metal contaminants in fertilizers and other soil amendments used in agriculture. Selected commercial fertilizers, lime products, and dairy manures were sampled, digested with hydrofluoric acid mixtures, and analyzed for trace element contaminants by inductively coupled plasma–mass spectrometry (ICP–MS). The trace element and heavy metal concentrations of the commercial fertilizers tested were generally low, although the phosphate component of fertilizer blends contained measurable concentrations of several elements of concern, including cadmium (Cd), uranium (U), arsenic (As), and molybdenum (Mo). At the concentrations in these fertilizers, agronomic rates of application would take decades to significantly increase soil concentrations of these elements above background. The manures were found on average to have low concentrations of all trace elements and heavy metals measured, with the important exceptions of copper (Cu) and zinc (Zn), where feed additives and use of Cu sulfate in treating hoof rot may explain the highest concentrations measured. Annual loadings of about 0.35 kg ha−1 Cu and 0.9 kg ha−1 Zn to dairy farmland are estimated for the median manure composition. Concentrations of lead (Pb), cadmium (Cd), and mercury (Hg) did not exceed 4.3, 0.4, and 0.05 mg kg−1 (dry weight), respectively, in any manure sample. Correlation of manure Pb concentration to aluminum (Al), indicates that soil contamination of the manure accounts for most of the Pb.

An evaluation of extractants for assessment of metal phytoavailability to guide reclamation practices in acidic soilscapes in northern regions

Abedin, J., Beckett, P. and Spiers, G. 2012. An evaluation of extractants for assessment of metal phytoavailability to guide reclamation practices in acidic soilscapes in northern regions. Can. J. Soil Sci. 92: 253-268. Although soil organic matter and nutrient bioavailability in metal-impacted soilscapes of Sudbury, Ontario, are potentially limiting full ecological recovery, total metal content was used as the critical driver for a 2008 ecological risk assessment. The current greenhouse study evaluated chemical extractants to predict bioavailability of nutrients and contaminant metals to indigenous grasses (Deschampsia). Single extraction methods (0.01 M strontium nitrate, water, 0.01 M calcium chloride, 0.1 M sodium nitrate, 1.0 M ammonium nitrate, 0.1 M lithium nitrate, 1.0 M magnesium chloride, 0.11 M acetic acid, 1.0 M ammonium acetate, 0.05 M ammonium-EDTA, pore water) were examined to assess availability of potentially phytotoxic metals and nutrients in smelter-impacted soils. Extraction procedures to predict phytoavailability were either soil concentration or plant tissue concentration and element dependent. Total and extractable metal concentrations were more correlated for regional contaminant metals (e.g., copper, lead, arsenic, selenium) released by the smelting industry than non-contaminant ones (e.g., iron, calcium, potassium, boron, zinc, molybdenum). The lack of relationship between total and extractable concentrations for most non-contaminant metals suggests total concentration is not a good indicator of phytoavailability for nutrient elements. Stronger correlations between shoot tissue and extractable concentrations were observed for less aggressive extractants (pore water, water, lithium nitrate) reflecting their suitability in predicting phytoavailability over most aggressive ones (except ammonium nitrate).

Total and bioavailable metals in two contrasting mining regions (Sudbury in Canada and Lubumbashi in DR-Congo): relation to genetic variation in plant populations

Knowledge of total and bioavailable metal contents in soil is important for regional risk assessment and management. The main objective of the present study was to analyse the concentrations of metals in soils in two contrasting mining regions (Sudbury in Canada and Lubumbashi in DR-Congo). Genetic variation of plant populations was investigated to assess the potential impact of metal contamination on forest sustainability. The levels of copper, cobalt, zinc, arsenic, and lead were significantly higher (up to 200-fold) in mining sites in the Lubumbashi compared to the most highly contaminated Sudbury sites. The nickel content in soil samples from Lubumbashi was much lower compared to Sudbury region samples. Only 3.5% and 4 % of total copper and nickel, respectively, were phytoavailable, with values of 6%, 5.7%, 3.6%, and 5.4% for cobalt, magnesium, manganese, and zinc, respectively. There were significant positive correlations between total metal and phytoavailable metal concentrations for copper (r=0.99), nickel (r=0.86), cobalt (r=0.72), strontium (r=0.71), and zinc (r=0.66). Although genetic variation was high in Picea glauca populations from the Sudbury region, no association was found between metal contamination levels and genetic variation within and among the P. glauca populations.

Effects of estimates from different geochemical models on metal fate predicted by coupled speciation‐fate models

Coupled metal speciation-fate models are an improvement over stand-alone fate-transport models for accurately assessing metal fate and transport. These coupled models estimate fate-controlling partition coefficients using geochemical speciation/complexation models. Commercially available geochemical models are practical options for a two-step, loose coupling with fate-transport models. These models differ in their partitioning estimates because of differences in assumptions, databases, and so on. The present study examines the effects of differences in estimates from geochemical models on estimates of cationic metal fate using two geochemical models: the Windermere humic aqueous model (WHAM) and the minicomputer equilibrium+ model (MINEQL+). The results from each geochemical model were used as input to the fate module of TRANSPEC (a general, coupled metal transport and speciation model). The two versions of the TRANSPEC model were then used to assess the fate of five cationic metals (Cd, Cu, Ni, Pb, and Zn) in Ross Lake (Flin Flon, MB, Canada; alkaline, eutrophic, mine impacted), Kelly Lake (Sudbury, ON, Canada; circumneutral, mesotrophic, mine influenced), and Lake Tantaré (Quebec City, QC, Canada; acidic, oligotrophic, pristine). For relatively soluble metals (Cd, Ni, and Zn), the WHAM and MINEQL+ estimates of speciation/complexation were similar for Ross and Kelly lakes but differed for Lake Tantaré. These differences, however, did not result in significant differences in overall fate estimates. Marked differences were observed between the WHAM and MINEQL+ estimates of partition coefficient, Kd, for more particle-reactive Cu and Pb that translated into the greatest impact on fate in mesotrophic Kelly Lake, in which particle movement is important for fate.

X-ray μCT imaging technique reveals corm microstructures of an arctic-boreal cotton-sedge, Eriophorum vaginatum

X-ray computed tomography (CT), a non-destructive imaging technique, has recently been effectively applied to botanical research. In this study an X-ray microCT technique was developed to allow for anatomical study of the overwintering corms of Eriophorum vaginatum, an ecologically important sedge species in arctic tussock-tundra and boreal peatlands. Using a GE Medical MS8X-130 X-ray microCT scanner, optimal imaging parameters included scanning isolated corms at 80 k Vp and 100 microA with a 3500 ms exposure time and an isotropic voxel size of 10 microm. A Gaussian blur image filter with a blur radius (sigma) of two pixels was applied to the optimal dataset to improve visual detection and contrast of tissues while removing 99.2% of image noise. Using the developed X-ray microCT technique several undocumented anatomical characteristics of the corm were identified including the vascular connection between a parent corm and branching cormel and the 3D shape of sclereid clusters. The 3D structure of sclereid clusters was determined whereby the perimeter of their lance shape is greatly reinforced by sclereids with thicker secondary cell walls as compared to those of the interior of the cluster. The structure of sclereid clusters and their association with leaf traces suggests they may be stabilizing the corm-leaf connection to protect vascular tissues from physical damage. The proposed X-ray microCT technique is an excellent tool for determination of the 3D structure of E. vaginatum corms and may be used to detect alterations in tissue structure and chemistry in response to environmental change in this and other Cyperaceous species.

Multi-dimensional water quality assessment of an urban drinking water source elucidated by high resolution underwater towed vehicle mapping

Spatial surveys of Ramsey Lake, Sudbury, Ontario water quality were conducted using an innovative underwater towed vehicle (UTV) equipped with a multi-parameter probe providing real-time water quality data. The UTV revealed underwater vent sites through high resolution monitoring of different spatial chemical characteristics using common sensors (turbidity, chloride, dissolved oxygen, and oxidation/reduction sensors) that would not be feasible with traditional water sampling methods. Multi-parameter probe vent site identification is supported by elevated alkalinity and silica concentrations at these sites. The identified groundwater vent sites appear to be controlled by bedrock fractures that transport water from different sources with different contaminants of concern. Elevated contaminants, such as, arsenic and nickel and/or nutrient concentrations are evident at the vent sites, illustrating the potential of these sources to degrade water quality.

Radionuclide release from simulated waste material after biogeochemical leaching of uraniferous mineral samples

Biogeochemical mineral dissolution is a promising method for the released of metals in low-grade host mineralization that contain sulphidic minerals. The application of biogeochemical mineral dissolution to engineered leach heap piles in the Elliot Lake region may be considered as a promising passive technology for the economic recovery of low grade Uranium-bearing ores. In the current investigation, the decrease of radiological activity of uraniferous mineral material after biogeochemical mineral dissolution is quantified by gamma spectroscopy and compared to the results from digestion/ICP-MS analysis of the ore materials to determine if gamma spectroscopy is a simple, viable alternative quantification method for heavy nuclides. The potential release of Uranium (U) and Radium-226 ((226)Ra) to the aqueous environment from samples that have been treated to represent various stages of leaching and passive closure processes are assessed. Dissolution of U from the solid phase has occurred during biogeochemical mineral dissolution in the presence of Acidithiobacillus ferrooxidans, with gamma spectroscopy indicating an 84% decrease in Uranium-235 ((235)U) content, a value in accordance with the data obtained by dissolution chemistry. Gamma spectroscopy data indicate that only 30% of the (226)Ra was removed during the biogeochemical mineral dissolution. Chemical inhibition and passivation treatments of waste materials following the biogeochemical mineral dissolution offer greater protection against residual U and (226)Ra leaching. Pacified samples resist the release of (226)Ra contained in the mineral phase and may offer more protection to the aqueous environment for the long term, compared to untreated or inhibited residues, and should be taken into account for future decommissioning.

Variation in whole DNA methylation in red maple ( Acer rubrum ) populations from a mining region: association with metal contamination and cation exchange capacity (CEC) in podzolic soils

Although a number of publications have provided convincing evidence that abiotic stresses such as drought and high salinity are involved in DNA methylation reports on the effects of metal contamination, pH, and cation exchange on DNA modifications are limited. The main objective of the present study is to determine the relationship between metal contamination and Cation exchange capacity (CEC) on whole DNA modifications. Metal analysis confirms that nickel and copper are the main contaminants in sampled sites within the Greater Sudbury Region (Ontario, Canada) and liming has increased soil pH significantly even after 30 years following dolomitic limestone applications. The estimated CEC values varied significantly among sites, ranging between 1.8 and 10.5 cmol(+) kg−1, with a strong relationship being observed between CEC and pH (r = 0.96**). Cation exchange capacity, significantly lower in highly metal contaminated sites compared to both reference and less contaminated sites, was higher in the higher organic matter limed compared to unlimed sites. There was a significant variation in the level of cytosine methylation among the metal-contaminated sites. Significant and strong negative correlations between [5mdC]/[dG] and bioavailable nickel (r = −0.71**) or copper (r = −0.72**) contents were observed. The analysis of genomic DNA for adenine methylation in this study showed a very low level of [6N-mdA]/dT] in Acer rubrum plants analyzed ranging from 0 to 0.08%. Significant and very strong positive correlation was observed between [6N-mdA]/dT] and soil bioavailable nickel (r = 0.78**) and copper (r = 0.88**) content. This suggests that the increased bioavailable metal levels associated with contamination by nickel and copper particulates are associated with cytosine and adenine methylation.

Successes in Application of Biotechnologies to Mine Land Remediation in the Russian Sub-Arctic

Abstract Sub-Arctic regions, previously considered one of the largest pristine ecosystems in the world, are being subjected to increasing pressure from mining and smelting activities. The minerals industry has contributed significantly to environmental damage and deterioration in the Russian sub-Arctic. Despite a significant reduction in gaseous and particulate emissions in the recent decades, the continuing air pollution and accumulation of potentially toxic metal levels in surface soils have promoted soil erosion and nutrient depletion in topsoils that inhibit vegetation recovery near the industrial complexes in the Kola Peninsula. These cumulative impacts on regional ecosystems are further exacerbated by the changing climatic conditions. The effectiveness of rehabilitation programs initiated in 2003–04 is largely dependent on the ongoing decrease of pollutant loadings, on the improvement of physical, chemical, and biological conditions of regional soils, and also on the effectiveness and suitability of the evolving remediation technology. The pace of rehabilitation using diversified and newly developed improved remediation technologies to enhance sustainable environmental management and regional economic development needs to be accelerated.

Rates and processes affecting As speciation and mobility in lake sediments during aging

Sediments from an arsenic (As) contaminated groundwater vent site were used to investigate As(III) binding, transformation and redistribution in native and iron oxide amended lake sediments using aging spiked batch reactions and a sequential extraction procedure that maintains As(V) and As(III) speciation. In the native sediments, fractionation analysis revealed that 10% of the spiked As(III) remained intact after a 32-day aging experiment and was predominantly adsorbed to the strongly sorbed (NH4H2PO4 extractable) and amorphous Fe oxide bound (H3PO4 extractable) fractions. Kinetic modelling of the experimental results allowed identifying the dominant reaction path for depletion of dissolved As(III) to As(III) absorbed on to the solid phase, followed by oxidation in the solid phase. Arsenite was initially adsorbed primarily to the easily exchangeable fraction ((NH4)2SO4 extractable), then rapidly transformed into As(V) and redistributed to the strongly sorbed and amorphous Fe oxide bound fractions. Oxidation of As(III) in recalcitrant fractions was less efficient. The iron oxide amendments illustrated the controls that iron oxides can have on As(III) binding and transformation rates. In goethite amended samples As(III) oxidation was faster and primarily occurred in the strongly sorbed and amorphous Fe oxide bound fractions. In these samples, 19.3μg Mn was redistributed (compared to the native sediment) from the easily exchangeable and crystalline Fe oxide bound fractions to the strongly sorbed and amorphous Fe oxide bound fractions, indicating that goethite may act as a catalyst for Mn(II) oxidation, thereby producing sorbed Mn(III/IV), which then appears to be involved in rapidly oxidizing As(III).