Ecotoxicity of Mine Tailings: Unrehabilitated Versus Rehabilitated

Earthworms are bioindicators of soil pollution. The ecotoxicity of tailings from selected gold mines in South Africa was investigated utilizing Eisenia andrei bioassays and biomarkers. Samples were obtained from unrehabilitated, rehabilitated and naturally vegetated sites. Biomass, neutral red retention time (NRRT), survival and reproduction were assessed using standardized protocols. Earthworm biomass, NRRT and reproductive success in rehabilitated tailings (comparable to naturally vegetated site) were significantly higher (p?<?0.05) than in unrehabilitated tailings. In addition, significantly lower (p?<?0.05) body tissue concentrations of As, Cd, Co, Cu and Ni contents were found in the rehabilitated tailings compared to the unrehabilitated. Further, significantly lower (p?<?0.05) soil Mn and Zn concentrations were obtained in unrehabilitated tailings than the rehabilitated and naturally vegetated sites. Overall, reduced ecotoxicity effects were confirmed in rehabilitated compared to unrehabilitated tailings. This suggests that rehabilitation as a post-mining restorative strategy has strong positive influence on mine tailings.     

Effects of Mining Activities on Heavy Metal Concentrations in Water,Sediment, and Macroinvertebrates in Different Reaches of the Pilcomayo River,South America

From 1997 until 1999 the extent and the ecological effects of zinc, copper, lead, and cadmium pollution were studied in different reaches of the South American Pilcomayo River. A comparison of metal concentrations in water, sediment, and chironomid larvae, as well as the diversity of macroinvertebrate species, was made between sites near the origin of the Pilcomayo River, with hardly any mining activities, sites in the Potosí region, with intensive mining, and sites located 500 km or further downstream of Potosí, in the Chaco plain. Samples were also collected in an unpolluted river (Cachi Mayu River) and in the Tarapaya River, which is strongly contaminated by mine tailings (1000 tons a day). The upper parts of the Pilcomayo River are strongly affected by the release of mine tailings from the Potosí mines where mean concentrations of lead, cadmium, copper, and zinc in water, filtered water, sediment, and chironomid larvae were up to a thousand times higher than the local background levels. The diversity of the benthic macroinvertebrate community was strongly reduced in the contaminated parts; 97% of the benthic macroinvertebrates consisted of chironomid larvae. The degree of contamination in the lower reaches of the river, however, was fairly low because of sedimentation processes and the strong dilution of mine tailings with enormous amounts of clean sediment from erosion processes. Analysis of sediment cores from the Ibibobo floodplain, however, reveal an increase of the heavy metal concentrations in the lower reaches since the introduction of the contaminating flotation process in the mine industry in 1985. Received: 7 March 2002/Accepted: 19 August 2002     

Assessing the toxicity of contaminated soils using the nematode Caenorhabditis elegans as test organism

In this study, nine uncontaminated reference soils and 22 contaminated soils with different physico-chemical properties and contamination patterns were tested with a standardized toxicity test, using the nematode, Caenorhabditis elegans, as test organism. Fertility, growth and reproduction of C. elegans in the soils were compared with the exposure in standard soil Lufa St.2.2. C. elegans showed 100% fertility and a very low variability of growth in the reference soils. Although, reproduction varied considerably between the various reference soils, validity criteria (>30 offspring per test organism) were met in all reference soils. Moreover, Lufa St. 2.2 turned out to be a suitable and representative control soil. In order to clearly classify the effects of the polluted soils on C. elegans, toxicity thresholds were derived for nematode fertility (20% inhibition), growth (10% inhibition) and reproduction (40% inhibition) on the basis of the test inherent variability (MDD=minimal detectable difference), as well as their variability between the uncontaminated reference soils (MTI=maximal tolerable inhibition). The contaminated soils showed clear toxic effects on the nematodes, whereas the toxicity was better correlated to organic than to heavy metal contamination in bulk soil. Interestingly, the results of the nematode toxicity test were not well correlated with those of tests with oligochaetes, collembolans and plants, performed with the same soils, showing that the results are not redundant. The toxicity test using C. elegans turned out to be suitable for testing the toxicity of field collected soils and might by a valuable addition to soil test batteries.     

Prosopis pubescens (Screw Bean Mesquite) Seedlings are Hyperaccumulators of Copper

Due to health reasons, toxic metals must be removed from soils contaminated by mine tailings and smelter activities. The phytoremediation potential of Prosopis pubescens (screw bean mesquite) was examined by use of inductively-coupled plasma optical emission spectroscopy. Transmission electron microscopy was used to observe ultrastructural changes of parenchymal cells of leaves in the presence of copper. Elemental analysis was used to localize copper within leaves. A 600-ppm copper sulfate exposure to seedlings for 24 days resulted in 31,000 ppm copper in roots, 17,000 ppm in stems, 11,000 in cotyledons and 20 ppm in the true leaves. For a plant to be considered a hyperaccumulator, the plant must accumulate a leaf-to-root ratio <1. Screw bean mesquite exposed to copper had a leaf-to-root ratio of 0.355 when cotyledons were included. We showed that P. pubescens grown in soil is a hyperaccumulator of copper. We recommend that this plant should be field tested.     

Metal Tolerance Capability of <Emphasis Type="Italic">Helichrysum microphyllum</Emphasis> Cambess. subsp. <Emphasis Type="Italic">tyrrhenicum</Emphasis> Bacch., Brullo &amp; Giusso: A Candidate for Phytostabilization in Abandoned Mine Sites

Sardinia was known as an important mine pole in Europe during his history. Still after decades from mine closure, 75.000.000 m³ of mine waste, rich in heavy metals, were left abandoned causing a huge environmental legacy on the mine district area. Consequently, cost effective remediation is required. In this frame, phytoremediation is considered a feasible candidate. This research was focused on Helichrysum microphyllum subsp. tyrrhenicum, which is pioneer in xeric soils with low-functions, like mine tailings. The aim of this study was to evaluate its ability to extract heavy metals from mine soils and accumulate them in plant tissues and its suitability for phytostabilization. Sundry samples of soil, roots and epigean organ were collected through field sampling and analysed in order to obtain metals concentration and mineralogical characteristics. Our results indicate that this species tolerates high concentration of zinc, lead and cadmium, behaving as a species suitable for phytostabilization.     

Spatial-based assessment of metal contamination in agricultural soils near an abandoned copper mine of eastern China

An investigation about metal contamination on agricultural soils was carried out near an abandoned copper mine in eastern China. Results showed the average concentrations of Cu, Pb, Zn and Cd in the 155 soil samples were 147, 53.8, 158, 0.32 mg kg⁻¹ respectively, which were 4.6-, 2.2-, 2-, 1.7-fold of the corresponding background value. According to the Chinese Farmland Environmental Quality Evaluation Standards for Edible Agricultural Products, it was found 18.4 % of the soils belonged to heavily and moderately contaminated soils.     

Spatial patterns of dispersion and pollution sources for arsenic at Lousal mine, Portugal

This study uses geostatistical modelling to identify hot spots of metal contamination produced by hazardous mining tailings from an inoperative Portuguese mine. Lousal is one of the many massive sulphide deposits of the Iberian Pyrite Belt. The mine is now closed, but the heavy metal enriched tailings remain at the site. Applying geostatistics to the diagnosis of this potentially contaminated area we aim to assess the quality of the soil, namely through a risk probability mapping for arsenic, for a better knowledge about the vulnerability of the soil to arsenic contamination. To achieve this aim, the initial variable was transformed into two indicator variables using the risk-based standards (intervention values) for soils, as proposed by Swartjes (1999), as the limit value. To account for the spatial structure, sample variograms were computed for the main directions of the sampling grid and a spherical model was fitted to the variables (arsenic raw data and indicator variables). The parameters of the model were used in the estimation process. To assess the vulnerability of the soil towards the mining works, a soil quality probability mapping for arsenic was carried out showing contamination probabilities in the area. The use of indicator kriging, as an alternative to other more complex kriging methods, in the soil data of the Lousal mine, produced unbiased soil quality maps.     

Using earthworms to test the efficiency of remediation of oil-polluted soil in tropical Mexico

This study focuses on the medium-term effects of soil bioremediation on mortality and reproduction rates of Eisenia fetida (laboratory experiment) and of the tropical earthworm Polypheretima elongata (field experiment). We compared soils restored with the two bioremediation technologies landfarming (LF) and compost-bioremediation (BI) with control soils and with soils contaminated with 1% and 2% of petroleum. Control and restored soils both were fertile and showed low hydrocarbon contents. The mortality of E. fetida was not influenced by soil restoration and by contamination with 1% petroleum; it only increased in soils contaminated with 2% petroleum. However, the reproduction rate of E. fetida was significantly lower in the soils restored with LF and in those contaminated with 1% crude oil and significantly higher in the soils restored with BI. P. elongata showed the same reaction as E. fetida. We conclude that it is important to include reproduction or other sub-lethal tests for earthworms when estimating the efficiency of restoration techniques.     

Utilizing an Earthworm Bioassay (Eisenia andrei) to Assess a South African Soil Screening Value with Regards to Effects from a Copper Manufacturing Industry

Metal contamination of soil due to industrialization has become an increasingly important problem in South Africa. This study aimed to investigate the potential impact of a copper (CuSO₄·5H₂O) production company on the soil environment. Bioassays using Eisenia andrei were performed to assess changes in biomass, reproduction and a biomarker, neutral red retention time, over a 28 day period. Earthworms exposed to soils from the Cu production site differed significantly (p < 0.05) from those exposed to soils 500 m and 5 km away in terms of the measured endpoints. These findings are consistent with the results from the chemical analysis which showed an elevated soil Cu content for both sites closest to the chemical production company compared to the reference site. The results confirm the importance and predictive value of using bioassays in conjunction with chemical analysis during soil quality assessments.     

Spatial Variability of Metal Bioaccumulation in Estuarine Killifish (Fundulus heteroclitus) at the Callahan Mine Superfund Site, Brooksville, ME

The former Callahan Mine Site in Brooksville, ME, is an open-pit, hardrock mine site in an intertidal system, thus providing a unique opportunity to evaluate how metal-enriched sediments and overlying water impact estuarine food webs. Copper, zinc, cadmium, and lead concentrations in sediment, whole water, and Atlantic killifish (Fundulus heteroclitus) were evaluated at sites in Goose Pond (GP; Callahan Mine Site) and at reference sites. The metal concentrations of sediment, water, and fish were spatially distinct and significantly greater at the mine site than in the reference estuary. Sediment concentrations were particularly elevated and were above probable effects levels for all four metals adjacent to the tailings pile. Even in this well-mixed system, water metal concentrations were significantly elevated adjacent to the tailings pile, and concentrations of Cu and Zn were above ambient water-quality criteria for chronic marine exposure. Neither organic matter in the sediment nor salinity or pH of the water explained the metal concentrations. Adjacent to the tailings pile, killifish metal body burdens were elevated and were significantly related to both sediment and aqueous concentrations. In conclusion, (1) the contaminated sediment and seepage from the tailings impoundment and waste rock pile no. 3 create a continual flux of metals into the water column, (2) the metals are bioavailable and bioconcentrating as evident in the killifish tissue concentrations, and (3) Callahan Mine is directly affecting metal bioaccumulation in fauna residing in the GP estuary and, potentially, in Penobscot Bay by the way of “trophic nekton relay.”     

Ecological Risk Assessment of Neodymium and Yttrium on Rare Earth Element Mine Sites in Ganzhou,China

Nowadays rare earth elements (REEs) are widely applied in high-technology and clean energy products, but their environmental risks are still largely unknown. To estimate the ecological risk of REEs, soil samples were collected from REE mine tailings with and without phytoremediation. The results showed that the tailings had rather low organic matter and high total REE concentrations, up to 808.5 mg/kg. The 10% effective concentration (EC10) of neodymium (Nd) and yttrium (Y) were calculated based on the toxicity tests of seed germination and root growth. For both wheat and mung bean, the EC10 of Nd and Y in soils were in the range of 1053.1–1300.1 mg/kg. The average hazard quotient of mine tailing soil without phytoremediation was higher than that with phytoremediation. All the hazard quotient of Nd and Y were less than 1, indicating that Nd or Y alone was unlikely to cause adverse ecological effects. Given to the coexistence of REEs on mine sites, the ecological risk of REE mixture could be potentially high towards local soil environments, even for soils with phytoremdiation.

     

Effects of copper on phenology and reproduction in Rumex dentatus from metalliferous and non-metalliferous sites

The responses of phenology and reproductive traits to copper stress in two populations of Rumex dentatus were comparatively studied with pot culture experiments. Seeds used for the experiments were, respectively, collected from metalliferous and normal soils. It was found that the responses of phenology and reproductive traits to Cu treatment between the two populations were significantly different. Compared to the non-metallicolous population, the metallicolous population of R. dentatus had a short life cycle, large reproductive effort, and high fertility under Cu stress. In addition, the reproductive effort in metallicolous population of R. dentatus was maintained at the expense of a curtailment of vegetative development. The results suggested that change in phenological traits and more resources allocation to reproduction might play an important role in the adaptation of metallicolous population of R. dentatus to the Cu-enriched mine soils.     

Effect of leaching and aging on the bioavailability of lead to the springtail Folsomia candida

Because it is unclear if leaching can account for differences in metal bioavailability observed between metal-spiked soils and historically contaminated field soils, we simultaneously assessed Pb toxicity to the springtail Folsomia candida in three transects of Pb-contaminated soils and in leached and unleached soils spiked at similar total Pb concentrations. Total Pb concentrations of 3,877 mg/kg dry weight and higher always caused significant effects on F. candida reproduction in the spiked soils. In the transects, only the soil with the highest Pb concentration of 14,436 mg/kg dry weight significantly affected reproduction. When expressed as pore-water concentrations, reproduction was never significantly affected at Pb concentrations of 0.539 mg/L, whereas reproduction was always significantly affected at Pb concentrations of 0.678 mg/L and higher, independent of the soil treatment. These results indicate that pore-water Pb concentrations can explain, at least in part, the observed differences in the toxicity data expressed as total Pb concentrations. Leaching after the spiking procedure only caused small differences in Pb toxicity and, therefore, cannot account for toxicity differences between laboratory-spiked soils and historically contaminated field soils.     

Toxicity to Eisenia andrei and Folsomia candida of a metal mixture applied to soil directly or via an organic matrix

Regulatory limits for chemicals and ecological risk assessment are usually based on the effects of single compounds, not taking into account mixture effects. The ecotoxicity of metal-contaminated sludge may, however, not only be due to its metal content. Both the sludge matrix and the presence of other toxicants may mitigate or promote metal toxicity. To test this assumption, the toxicity of soils recently amended with an industrial sludge predominantly contaminated with chromium, copper, nickel, and zinc and soils freshly spiked with the same mixture of metals was evaluated through earthworm (Eisenia andrei) and collembolan (Folsomia candida) reproduction tests. The sludge was less toxic than the spiked metal mixture for E. andrei but more toxic for F. candida. Results obtained for the earthworms suggest a decrease in metal bioavailability promoted by the high organic matter content of the sludge. The higher toxicity of the sludge for F. candida was probably due to the additive toxic effect of other pollutants.     

Effect of soil properties on lead bioavailability and toxicity to earthworms

Soil properties are important factors modifying metal bioavailability to ecological receptors. Twenty-one soils with a wide range of soil properties (USA; http://soils.usda.gov/technical/classification/taxonomy/) were amended with a single concentration of Pb (2,000 mg/kg) to determine the effects of soil properties on Pb bioavailability and toxicity to earthworms. Earthworm mortality ranged from 0 to 100% acute mortality following exposure to the same total concentration of Pb (2,000 mg/kg) in amended field soils. Internal Pb concentrations in earthworms ranged from 28.7 to 782 mg/kg, with a mean of 271 mg/kg. Path analysis was used to partition correlations in an attempt to discern the relative contribution of each soil property. Results of path analysis indicated that pH was the most important soil property affecting earthworm mortality (p < 0.01) and internal Pb (p < 0.05). Soil pH was related inversely to mortality and internal Pb, soil solution Pb, and Pb bioavailability. The most important soil property modifying reproduction was amorphous iron and aluminum oxides (FEAL). Because FEAL is rich in pH-dependent cation-exchange sites, several soil properties, including pH, FEAL, and cation-exchange capacity, have a causal effect on Pb adsorption and soluble Pb. Path analysis is useful for assessing contaminated soils with a wide range of soil properties and can assist in ecological risk assessment and remediation decisions for contaminated sites. Soil properties are important factors modifying metal bioavailability and toxicity and should be considered during the ecological risk assessment of metals in contaminated soils.     

High prevalence of respiratory symptoms among workers in the development section of a manually operated coal mine in a developing country: A cross sectional study

Background  

Few studies of miners have been carried out in African countries; most are from South Africa, where the working conditions are assumed to be better than in the rest of Africa. Several studies have focused on respiratory disorders among miners, but development workers responsible for creating underground road ways have not been studied explicitly. This is the first study assessing the associations between exposure to dust and quartz and respiratory symptoms among coal mine workers in a manually operated coal mine in Tanzania, focusing on development workers, as they have the highest exposure to coal dust.     

The radiological impact of mining in a Th-rich Norwegian area

The radiological impact of former mining activities in the Fen area in southern Norway has been assessed. The area is known to have enhanced concentrations of Th. A recent epidemiological study suggested a significant increment of lung cancer among the former miners, and the doses to the miners have been assessed. The main contributor to the effective dose equivalent in one of the mines was inhaled 220Rn progeny. Water in drilled wells and in nearby lakes has been analysed for 220Rn and Ra. Uranium and Th analyses were performed on mine and lake water. The mining activity does not seem to have contaminated drinking water significantly. The tailings from Nb production has enriched Ra and Th concentrations. The tailings and the possible use of waste rock from the mining are probably the most important environmental results of the mining activities.     

Completing the cycle: Haemaphysalis elliptica,the vector of Babesia rossi,is the most prevalent tick infesting black-backed jackals (Canis mesomelas), an indigenous reservoir host of B. rossi in South Africa

In sub-Saharan Africa, virulent babesiosis in domestic dogs is primarily caused by Babesia rossi. Black-backed jackals (Canis mesomelas), indigenous hosts of B. rossi, are the most likely reservoir from which B. rossi became established in domestic dog populations in South Africa. Haemaphysalis elliptica is the only confirmed vector transmitting B. rossi to domestic dogs; very little was known about the prevalence of H. elliptica infestation in black-backed jackal populations. All jackals (n = 9) from a site in Gauteng Province, South Africa, were infested with H. elliptica, which was also the most numerous tick recovered. Rhipicephalus simus was the second-most prevalent tick. Low numbers of four other tick species were recovered. An extended dataset (n = 23) including published data on adult black-backed jackals (n = 14) from other parts of South Africa indicated that H. elliptica (74%) was the most prevalent species, followed by R. simus (44%). Published data from black-backed jackals (n = 12) in Kenya showed a prevalence of H. leachi sensu lato infestation of 93%. We conclude that where its off-host ecological requirements are met, H. elliptica/leachi is the most prevalent tick infesting black-backed jackal population throughout their range. A comprehensive checklist, with discussion, is given for the 29 tick species reported from black-backed jackals in both southern and northeastern Africa.     

Increased Metal Concentrations in Giant Sungazer Lizards (Smaug giganteus) from Mining Areas in South Africa

Environmental contaminants from anthropogenic activity such as mining can have profound health effects on the animals living in adjacent areas. We investigated whether inorganic contaminants associated with gold-mining waste discharges were accumulated by a threatened species of lizard, Smaug giganteus, in South Africa. Lizards were sampled from two mining sites and two control sites. Blood samples from the most contaminated mining site had significantly greater concentrations of lithium, sodium, aluminum, sulfur, silicon, chromium, manganese, iron, nickel, copper, tungsten, and bismuth than the remaining sites. Contaminant concentrations were not significantly related to lizard body condition, although these relationships were consistently negative. The adult sex ratio of the population inhabiting the most contaminated site also deviated from an expected 1:1 ratio in favour of female lizards. We demonstrate that lizards at these mining sites contained high concentrations of heavy metals that may be imposing as yet poorly understood costs to these lizards.     

Unexpected reduction in reproduction of Collembola exposed to an arsenic-contaminated soil

To assess the problems posed by ecological testing of the toxicity of polluted soils, we applied the Collembola reproduction test to the soil from a mining site polluted by metals. Our aim was to quantify the chronic toxicity of contaminated soil using the Folsomia candida reproduction test. Briefly, the polluted soil, which contains in particular large quantities of arsenic, is mixed in various proportions with a reference soil, and the number of juveniles is counted five weeks later. The results were quite unexpected in that a stronger effect was observed on reproduction with dilute contaminated soil, 0.78 to 3.1%, than with much higher concentrations. The pure contaminated soil is not highly toxic. Arsenic (As) dosage in pore water shows that a change in its bioavailability occurs that may explain the surprising toxicity results. As the main contaminant of the soil was arsenic, we showed that the lowest-observed-effect concentration and the median effective concentration of this metal for the reproduction of F. candida in International Organization for Standardization (Geneva, Switzerland) soil experimentally contaminated with arsenic were low (2.22 and 2.19 microg/g, respectively). Likewise, we showed that pH modifies the bioavailability and the toxicity of As, but we do not think that this parameter explains the test results. These results show that this bioassay should be used cautiously to test toxicity of polluted soils.