Mining Site Soil Research Articles

Working with complex natural systems sometimes calls for thinking outside the square

The two features in this issue tell of recovery of local ecosystems after thinking ‘outside the square’. The first is the case of Hinewai Reserve in New Zealand, owned and managed by the Maurice White Native Forest Trust, where the paper's author Hugh Wilson recognised that the colonising shrub Gorse (Ulex europaeus) facilitated rather than inhibited recovery by the site's prior species. The second is the case of East Trinity wetland, near Cairns Queensland, Australia where the Queensland Government has used lime-assisted tidal inundation to counter degradation severely degraded coastal acid sulphate soil created by ill-advised agriculture. In both cases, outstanding natural recovery has occurred to date and is continuing. There are many take home messages from these case studies – not only the obvious messages regarding potential to harness the resilience of local species to periods of stress and stress release but also messages regarding what is the appropriate level of intervention needed to achieve recovery. This emphasises that all restoration interventions are, in essence, methods of compensating for damage to ensure that natural recovery – the purpose and end result of all restoration – can recommence. Those lessons are obvious in projects where natural recovery is clearly the primary mechanism of reinstating biota; but they are less obvious in projects where all habitat features and biota have been depleted and timely recovery requires rebuilding habitats and reintroducing biota. In mine site restoration, for example, soils, habitat structure and biota usually need to be completely reintroduced; yet it is still rewarding to model interventions on mimicking natural conditions and processes; whether it include such things as preparations for germination and plant development (see Mayence and colleagues this issue) or importing woody debris to foster invertebrate recovery (see Lythe and colleagues). Ecological restoration and management requires us to avoid simplistic dogmas where they are not helpful. Not only does it behove us to question assumptions such as that only native plants can play a role in native recovery – but also assumptions such as that all natives necessarily behave in a manner conducive to the persistence of the broader native ecosystem. Barrett and colleagues, for example, find somewhat damaging levels of browsing by native fauna on an endangered ecological community in the Stirling Range in Western Australia and suggest potential management options. Thinking outside the square is also required to manage for unexpected threatened species in recovering mine sites (Craig and colleagues); differing fire regimes where threatened species share a habitat (Hunter); finding methods for detecting whether management is achieving appropriate conditions for target native fauna (Schultz and colleagues); and considering new funding models for ecological research (Dovers and colleagues). The paper in this issue reviewing progress with implementation of the Wunambal Gaambera People's Healthy Country Plan also signals the maturation of efforts to do things differently, adapting Conservation Action Planning to Indigenous land and sea management in ways that lead to specific conservation and culturally beneficial outcomes (see Austin and colleagues this issue). Just like in the case of Hinewai Reserve in New Zealand, Australian cases of private conservation management planning can be flexible enough to build capacity and ensure the planning and implementation is socially responsive and can be sustained over time.

Maize (Zea mays L.) performance in organically amended mine site soils

Organic amendments play an important role in the eco-friendly remediation of degraded mine site soils. This study investigated the quality (essential nutrients and heavy metal content) of maize grown on organically amended soils from three active mines in Nigeria. Soil samples were collected randomly at 0–15 cm depth, air-dried and sieved. Five kg of soil were amended with poultry manure and sawdust (poultry manure only, sawdust only, poultry manure-sawdust mixtures in 3:1, 2:1 and 1:1 ratios) at 10 g kg−1. Maize (Zea mays L.) seeds were planted and watered for two consecutive periods of 8 weeks, with the control and treatment experiments set up in the screenhouse in quadruples. Harvested tissues were weighed, dried, ground and digested. Chemical properties were determined using standard methods while atomic absorption spectrophotometry was used to determine total metal concentrations (Ca, Mg, Fe, Zn, Pb, Cd and Cu). ANOVA was used to test for significant differences among treatment groups in the various parameters. Application of poultry manure-sawdust mixtures significantly (p < 0.05) enhanced tissue dry matter yield, as well as N, P, K, and Na contents while Zn, Cd, Cu and Pb were immobilized to approximately 50–100%. Treatment with sawdust alone reduced tissue nutrient content resulting in depressed plant yield while poultry manure only though enhanced crop yield, contained higher heavy metal contents. Soil amendments comprised of poultry manure-sawdust mixtures can be effective remediation strategy for mine site soils, as these organic materials help replenish soil nutrients, immobilize heavy metals, and enhance food productivity.

Metallisation and environmental management of mining site soils

The present paper deals with the issue of technogenic metallisation of mining site soils and the biosphere as a whole. The natural biosphere metallisation has probably started long ago. It is connected with destruction of small areas with anomalously high content of metals in rocks and further migration of the released metals in the neighbouring biosphere areas. As a result, their content increases in a much larger area, although only slightly. This concentration increase can capture the pedosphere, hydrosphere, atmosphere, and living matter.As a result of deposit mining conducted by people, the enrichment of several biosphere parts with metals occurs much more intense and takes far greater areas than the natural metallisation. The metallisation began to have a negative impact on many living organisms, including humans. Therefore, the study and the role of this process from a purely geochemical moved into environmental. The investigation of topsoil pollution was conducted in mining areas of Russia, Kazakhstan, and Ukraine. The emission spectral analyses of thousands of samples showed that the dominant contemporary way of remediation at mining and beneficiation areas does not prevent a metal spread through the decades. The proposed insulation method allows preventing environmental pollution by using polyethylene and polypropylene wastes.

Screening for risk assessment around closed uranium mining sites

The aim of this study is to present the environmental impact and health risk 20 years after the closing of the uranium mining industry. The areas under observation are 31 former classical underground uranium mining and exploratory sites in Bulgaria. The geometric mean value of the gamma dose rate (0.33 μ Sv h -1 ), measured 1 m above ground in the mining sites, was three times higher than the mean of the gamma dose in the nearby settlements (0.11 μ Sv h -1 ). The geometric mean of specific activities for 238 U, 226 Ra, 232 Th, 40 K and 210 Pb in mining site soil was found to be: 437 Bq kg -1 , 291 Bq kg -1 , 65 Bq kg -1 , 835 Bq kg -1 and 318 Bq kg -1 , respectively. Analysis of variance and correlation were applied. The external dose and offsite external hazard index, as health risk indicators, were estimated based on the results. After twenty years there is still environmental contamination in some locations that may cause a health risk, so remediation and monitoring should continue and be maintained.

Microbial enzymes as an early warning management tool for monitoring mining site soils

Soil contamination may influence negatively soil health, which often limits and sometimes disqualifies soil biodiversity and decreases plant growth. However, the increased concentration and distribution of potentially toxic elements (PTEs) in soils by mismanagement of industrial activities, overuse of agrochemicals, and waste disposal are causing worldwide concern. This study focused at developing an early warning tool, based on a consortium of different microbial enzymes, for the assessment and monitoring of soil health in response to heavy metal pollution. Soils were collected from an abandoned mine area in northeast Italy, and the concentration of different heavy metals (Cr, Cu, Fe, Mn, Ni, Pb, Zn) were measured and analyzed. The results showed that soils affected by mining activities presented total Zn, Cu, Pb, and Fe concentrations above the internationally recommended permissible limits. A highly significant correlation occurred between the metal concentrations in soils (Fe, Pb, Zn, and Cu). Enzymatic activities varied proportionally with the level of heavy metals in soils and were negatively correlated: arylsulfatase (−0.55), leucine aminopeptidase (−0.12), β-glucosidase (−0.40), alkaline phosphatase (−0.35), and chitinase (−0.58). Conversely, microbial activities were positively correlated with organic matter content and microbial biomass. This study clearly highlights in situ interactions between different patterns of PTEs, represented by different combinations of heavy metals, and enzymatic activity of soil microbial communities, and demonstrate the type of interactions taking place between heavy metals, soil properties, and enzymatic activities. The assessment of changes in the activities of microbial community can precede some detectable changes in soil chemo-physical properties, and strongly support the utility of using enzymatic activity of soil microbial communities as an early warning tool for monitoring soil pollution with heavy metals.

Biosorption of Cadmium by Citrobacter sp. JH 11-2 Isolated from Mining Site Soil

The wide use of cadmium (Cd) in batteries and semiconductors poses human and environmental health hazards when these materials are disposed. Citrobacter sp. JH 11-2, isolated from soil at an abandoned mining site, shows potential for use as a biosorbent for Cd removal from aqueous solution. A minimal inhibitory concentration of 300 mg L−1 indicated high tolerance of the strain to Cd. The strain effectively removed 47.7% of the Cd from a 100 mg L−1 solution within 160 h. Cell fractioning revealed that most of the Cd (43.5%) was in the membrane fraction, while 38.5% was in the peptidoglycan layer and 18.0% was in the cytoplasmic fraction. Fourier transform infrared spectroscopy (FTIR) confirmed the presence of functional groups on dried Citrobacter sp. JH 11-2 cells that can adsorb or complex Cd ions. A Langmuir model provided a good fit to Cd removal by the cells, which followed pseudo-second-order kinetics. Results support further development of Citrobacter sp. JH 11-2 as a biosorbent for Cd removal.

Simultaneous Cr(VI) reduction and methylene blue removal by Bacillus sp. JH2-2 isolated from mining site soil

A Bacillus sp. strain (JH2-2), isolated from soil at an abandoned mine site, reduced Cr(VI) to Cr(III) under aerobic conditions. At pH 7, the strain reduced essentially all of the Cr(VI) in M9 minimal medium to Cr(III) at initial concentrations ≤50 mg Cr(VI) L−1 within 100 h. The X-ray diffraction pattern of the Cr(III) precipitate matched chromium (III) hydrogen phosphate (CrH2P3O10·2H2O). The JH2-2 strain showed high tolerance to other heavy metal(loid)s, with minimal inhibitory concentrations in liquid medium of (mg L−1): As (500), Cd (100), Cu (350), Ni (300), Zn (200), and Pb (1800). JH2-2 also promoted decolorization of methylene blue dye. Decolorization was faster in the presence of 10 mg Cr(VI) L−1 than in the absence of Cr(VI). A lag in decolorization at 30 and 50 mg Cr(VI) L−1 is likely due to initial toxicity and inhibition of bacterial growth. The chemistry of MB is complicated by its reduction to colorless leucomethylene blue, which can reoxidize to MB. However, aeration of the solution did not restore measurable MB, supporting removal of the dye via biosorption. Results indicate the bioremediation potential of Bacillus sp. JH2-2 for simultaneous Cr(VI) reduction and methylene blue removal from contaminated water.

Potential use of Pseudomonas koreensis AGB-1 in association with Miscanthus sinensis to remediate heavy metal(loid)-contaminated mining site soil

Endophytic bacteria have the potential to promote plant growth and heavy metal(loid) (HM) removal from contaminated soil. Pseudomonas koreensis AGB-1, isolated from roots of Miscanthus sinensis growing in mine-tailing soil, exhibited high tolerance to HMs and plant growth promoting traits. Transmission electron microscope (TEM) analysis revealed that AGB-1 sequestered HMs extracellularly and their accumulation was visible as dark metal complexes on bacterial surfaces and outside of the cells. DNA sequencing of HM resistance marker genes indicated high homology to the appropriate regions of the arsB, ACR3(1), aoxB, and bmtA determinants. Inoculating mining site soil with AGB-1 increased M. sinensis biomass by 54%, chlorophyll by 27%, and protein content by 28%. High superoxide dismutase and catalase activities, and the lower malondialdehyde content of plants growing in AGB-1-inoculated soil indicate reduced oxidative stress. Metal(loid) concentrations in roots and shoots of plants grown in inoculated soil were higher than those of the controls in pot trials with mine tailing soil. Results suggest that AGB-1 can be used in association with M. sinensis to promote phytostabilization and remediation of HM-contaminated sites.

Stabilization of Heavy Metals in Mining Site Soil with Silica Extracted from Corn Cob

Corn cob silica (CCS), produced via a modification of the sol-gel method, can reduce heavy metal availability and stabilize contaminated soil on abandoned mining sites. Adding 5 % (w/w) CCS to mining site soil increased pH from 4.0 to 7.7, and cation exchange capacity increased from 94.5 to 100.3 cmol+/kg. Sequential extraction showed that adding CCS decreased heavy metal availability in the soil. Mobility factor (MF) values indicated that CCS reduced Pb mobility more than that of Zn or Cu in all fractions. Pb concentrations in leachate from all fractions using the toxicity characteristic leaching procedure (TCLP) were greatly decreased by adding 3 % (w/w) CCS. CCS similarly reduced Zn concentrations in TCLP leachate. CCS addition did not impact Cu concentrations in leachate, likely because concentrations were much lower than those of the other metals. As was generally less mobile than the heavy metals; however, As mobility and leachability tended to increase with CCS addition because its oxyanions arsenite and arsenate have low affinity for negatively charged surfaces on the CCS. Shoot and root growth of Spinacia oleracea L. (spinach) was much greater in CCS-treated soil than in unamended soil. Results demonstrate the utility of CCS to stabilize heavy metals in contaminated mining site soil, but this treatment may not be ideal for As-contaminated soils.

Pseudomonas fluorescens JH 70-4 promotes Pb stabilization and early seedling growth of Sudan grass in contaminated mining site soil

A bacterial strain (JH 70-4) exhibiting plant growth promoting characteristics (indoleacetic acid production and 1-aminocyclopropane-1-carboxylate deaminase activity), as well as heavy metal(loid) (HM) tolerance and Pb precipitation, was isolated from HM-contaminated soil at an abandoned mine site. The bacterium was identified as Pseudomonas fluorescens based on 16S rDNA sequencing. The JH 70-4 strain induced precipitation of Pb as PbS nanoparticles, confirmed by X-ray diffraction. Solution pH, incubation time, and Pb concentration influenced removal and PbS formation. Inoculating contaminated soil with JH 70-4 decreased Pb availability; exchangeable Pb decreased while organic- and sulphide-bound Pb increased. The toxicity characteristic leaching procedure showed a 65% decrease in Pb in leachate 60 d after inoculating soil with JH 70-4. Shoot and root lengths of Sudan grass grown in the inoculated soil were greater than in the uninoculated soil. Findings suggest that microbial Pb fixation is a viable strategy for remediating soil and promoting plant growth for phytostabilization of contaminated sites.

Can earthworm-secreted calcium carbonate immobilise Zn in contaminated soils?

We investigated the interaction of soil Zn with calcium carbonate granules secreted by the earthworm Lumbricus terrestris. Earthworms were kept in agricultural soil amended with ZnSO4 to give Zn concentrations up to 750 mg kg−1 and in two former mine site soils containing 500 and 120 mg Zn kg−1. After 21–42 days the earthworms accumulated 260–470 mg Zn kg−1. Granule production was 0.027–2.11 mg CaCO3 earthworm−1 day−1 and was positively correlated with soil and soil solution pH (r = 0.66 and 0.85 respectively, p ≤ 0.01). Granule Zn concentration was 34–163 mg kg−1. Granules collected from Zn-free control soil and left in Zn-bearing soil for 28 days contained 49–60 mg Zn kg−1 suggesting that the majority of Zn associates with granules after their secretion. However, synchrotron X-ray fluorescence indicates some incorporation of Zn into granules during their formation. X-ray diffraction and X-ray absorption spectroscopy indicate that the granules are predominantly calcite and the spectroscopy suggests that the Zn is either adsorbed to, or incorporated into, the calcite lattice. X-ray diffraction of the outer c. 35 μm of the granules supports incorporation of Zn into the calcite lattice. The low granule production rates in the mine site soils and the granule Zn concentrations suggest that earthworm secreted calcium carbonate is unlikely to impact significantly on Zn mobility in soils.

Effects of nutrient and lime additions in mine site rehabilitation strategies on the accumulation of antimony and arsenic by native Australian plants

The effects of nutrient and lime additions on antimony (Sb) and arsenic (As) accumulation by native Australian and naturalised plants growing in two contaminated mine site soils (2735mgkg−1 and 4517mgkg−1 Sb; 826mgkg−1 and 1606 As mgkg−1) was investigated using a glasshouse pot experiment. The results indicated an increase in soil solution concentrations with nutrient addition in both soils and also with nutrient+lime addition for Sb in one soil. Metalloid concentrations in plant roots were significantly greater than concentrations in above ground plant parts. The metalloid transfer to above ground plant parts from the roots and from the soil was, however, low (ratio of leaf concentration/soil concentration≪1) for all species studied. Eucalyptus michaeliana was the most successful at colonisation with lowest metalloid transfer to above ground plant parts. Addition of nutrients and nutrients+lime to soils, in general, increased plant metalloid accumulation. Relative As accumulation was greater than that of Sb. All the plant species studied were suitable for consideration in the mine soil phytostabilisation strategies but lime additions should be limited and longer term trials also recommended.

Heavy metal pollution around Itakpe mine, Kogi State, Nigeria

The removal of large quantities of overburden through mining has resulted in the pollution of various ecosystems. Soil pollution around the Itakpe mine in Kogi State, Nigeria was studied through the determination of heavy metal concentration and chemical speciation of the metals cadmium (Cd), copper (Cu), magnesium (Mg), nickel (Ni), lead (Pb) and zinc (Zn) in soil using Flame Atomic Absorption Spectroscopy. Soil digestion was done with hydrofluoric-perchloric (HF-HClO4) acid mixture (5:1) and sequential extraction was carried out with different reagents in the extraction steps; Exchangeable, bound to carbonates, bound to Fe-Mn oxides, bound to organic matter and residual. Mean metal content of mining site soil is 0.16±0.02, 0.15±0.03, 0.04±0.02, 0.11±0.02, 0.07±0.01 and 0.04±0.03mg/g for Cd, Cu, Mg, Ni, Pb and Zn, respectively. Results of sequential extraction of the mining site soil show that the highest metallic levels were observed in the Fe-Mn, organic and residual fractions. Key words: Mine, heavy metals, tailings, pollution, agricultural soil.

In vitro assessment of arsenic bioaccessibility in contaminated (anthropogenic and geogenic) soils

Arsenic (As) bioaccessibility in contaminated soils (n=50) was assessed using the simplified bioaccessibility extraction test (SBET). Soils used in the study were collected from sites where As was used as an herbicide (railway corridor) or pesticide (cattle dip sites), from former gold mines and from highly mineralised locations containing geogenic As sources (gossans). In all but three soils, As bioaccessibility was less than 50% indicating that a significant proportion of the total As concentration may not be available for absorption in the gastrointestinal tract following incidental soil ingestion. When regression models were developed based on soil properties, the descriptive variables best able to describe As bioaccessibility in railway corridor, dip site and mine site soils were total As and total or dithionite-citrate extractable (free) iron (Fe). While As bioaccessibility could be predicted (r(2)=0.955, n=50) in these contaminated soils, As bioaccessibility for gossan soils was a poor fit using linear or multivariate regression analysis.

Arsenic Characterisation in Industrial Soils by Chemical Extractions

The purpose of this research was to find a reliable and easy to use method to characterise As in iron-rich industrial or mining site soils. In this objective classical sequential extraction schemes and single extractions with EDTA and phosphate solutions were used. Results showed that classical Tessier's scheme overestimated residual As. A scheme specific to anionic species was also not really suitable to evaluate As distribution in these iron-rich soils. A more complex scheme using specific iron reagents indicated a correlation between iron dissolution and arsenic leaching and these results were confirmed by single extractions with EDTA and oxalate solutions. Finally a simplified and less time consuming scheme was established, tested on diverse industrial soils and validated on a certified sediment reference material. It allowed evaluation in 24 hours of the easily extractable fraction, amount solubilized under reducing conditions and As strongly bound to the soil.

The reaction of copper ions and hypochlorite with minesite soils in relation to fungicidal activity

Phytophthora cinnamomi is a soil-borne pathogenic fungus and is the primary cause of dieback disease in the jarrah forests of south-west Western Australia. Treatments are needed to eliminate the fungus from infected soils. Compounds containing cupric ions (Cu2+) or hypochlorite (ClO-) have a known fungicidal activity against P. cinnamomi, but their efficacy is affected by soil factors. This study explores the possibility of containing P. cinnamomi by treatment of surface materials for haul roads at minesites in infected areas with these compounds. Solution concentrations of Cu2+ between 50 and 100 mg/L are considered to be fungicidally effective against P. cinnamomi. In samples from the lateritic regolith at the Huntly minesite of Alcoa in Western Australia, concentrations in this range are obtained after adding about 0-5 g (range = 0.3-1 g) of Cu2+ per kg of regolith material. Soil materials from mineral sand areas on the Swan Coastal Plain in Western Australia adsorb Cu2+ less strongly than the regolith materials from the Huntly minesite. Addition of about 0.1-0.2 g Cu2+ per kg is sufficient to reach a fungicidal concentration in solution in these soil materials. Movement of Cu2+ from treated surfaces of haul roads to groundwater and surface water can present a problem. For a single application, travel times of Cu2+ in both lateritic regolith and sandy soils were calculated to be = 200 years per metre. A single treatment of materials from the lateritic regolith would be effective for a period of 2-10 years, depending on the selected material. Sandy soils would have to be treated once or twice a year. Colloidal particles in both surface runoff and throughflow can contribute significantly to the spread of copper in the lateritic regolith, but much less in sandy soils. Hypochlorite is rapidly reduced to chloride by organic matter in soils. At additions of about 0.5 g ClO- per gram of organic carbon, however, hypochlorite can be an effective fungicide against P. cinnamomi.

Atmospheric Emission and Plant Uptake of Mercury from Agricultural Soils near the Almadén Mercury Mine

AbstractSurface soils collected near the Almadén, Spain, mercury mine reflected increasing concentrations of mercury (Hg) with proximity to the mine due to weathered mineral deposits and to atmospheric deposition of Hg from the smelter. Extractions with NaHCO3 or NH4OAc removed small amounts of Hg from both control (20 km from the mine; total Hg = 2.3 µg/g) and mine site soils (1 km; total Hg = 97 µg/g). Density gradient centrifugation indicated a significant fraction of the Hg to be associated with a high‐density mineral fraction, presumably cinnabar. Accumulation of Hg by alfalfa suggested a dual mechanism of uptake; roots accumulated Hg in proportion to the soil levels, while aerial plant material absorbed Hg vapor directly from the atmosphere. Soil fertilization with and without liming significantly increased total Hg uptake, largely due to plant growth stimulation. Liming itself had no significant effect. The rate of volatilization of elemental Hg from both soils (∼0.13 and 0.33 µg/m2 per hour at 25°C, for control and mine site, respectively) exceeded reported background emission rates by factors of 4 to 10, increasing with surface temperature and Hg content and decreasing with increased plant cover.