Fast simultaneous determination of traces of Cu(II) and Co(II) in soils and sediments with the luminol/perborate chemiluminescent system

A flow injection analysis method based on ion chromatography and luminol chemiluminescence detection was used for the simultaneous determination of copper (II) and cobalt (II) trace levels in soils and sediments following microwave-assisted acid digestion. Detection was based on chemiluminescence (CL) of the luminol–perborate system in an alkaline medium, which is catalyzed by both transition metals. The concentration and pH of the eluent (oxalic acid) was found to affect CL intensities and retention times, both of which were inversely proportional to the oxalic acid concentration. The calibration curves for both metal ions were linear and allowed a limit of detection of 0.003 μg l^?1 for cobalt (II) and 0.014 μg l^?1 for cooper (II) to be calculated. The proposed method was successfully used to determine both metal ions in certified reference materials of stream and river sediments and soil samples. Based on the results, the determination is free of interferences from the usual concomitant ions.     

Factors affecting accumulation of thallium and other trace elements in two wild Brassicaceae spontaneously growing on soils contaminated by tailings dam waste

Thallium is a scarce, highly toxic element. There are several investigations that report Tl accumulation in plants of the family Brassicaceae. These plants could pose a risk in areas where Tl is present at higher concentrations than normal soils. The present study reports analyses of two wild Brassicaceae, Hirschfeldia incana and Diplotaxis catholica, growing spontaneously at five sampling sites moderately polluted with Tl and other trace elements in the Green Corridor of the Guadiamar river, Seville, S. Spain. In general, trace element content was unremarkable in all part plants, despite the concentrations present in soil. Thallium was the only element whose concentration in both plant species was above normal for plants (maximum values of 5.00 mgkg(-1) in H. incana flowers). There were significant positive correlations between total Tl in soil and Tl in both plant species. Transfer Coefficients (TC) for all elements were, in general, <1 for both species, except for Tl in flowers and fruits at some sites. The highest Enrichment Factor (EF) was found for Tl in H. incana fruits (EF = 607) and D. catholica flowers (EF = 321). H. incana was studied in a previous growing season (2004) in the same area, although the rainfall was 3 times more than in the year of the present study (2005), giving a maximum Tl content of 46.5 mgkg(-1) in H. incana flowers. The data presented here show that Tl content of plants growing in semi-arid conditions can be significantly influenced by precipitation. In dry years, plant Tl accumulation may be significantly reduced.     

Carbon dioxide capture from combustion flue gases with a calcium oxide chemical loop. Experimental results and process development

Post-combustion carbonate looping processes are based on the capture of carbon dioxide from the flue gases of an existing power plant in a circulating fluidized bed reactor (CFB) of calcium oxide (the carbonator) particles. The calcination of calcium carbonate in a new oxy-fired CFBC power plant regenerates the sorbent (calcium oxide particles) and obtains high purity carbon dioxide. This communication presents experimental results from a small test facility (30 kWt) operated in continuous mode using two interconnected CFB reactors as carbonator and calciner. Capture efficiencies between 70 and 97% have been obtained under realistic flue gas conditions in the carbonator reactor (temperatures around 650 °C). The similarity between process conditions and those existing in CFBC power plants should allow a rapid scaling up of this technology. The next steps for this process development are also outlined.     

Response of Holm oak (Quercus ilex subsp. ballota) and mastic shrub (Pistacia lentiscus L.) seedlings to high concentrations of Cd and Tl in the rhizosphere

The impairment of root growth and photosynthetical functioning are the main impacts of trace elements on woody plant seedlings. In this work, we assessed the response of Holm oak (Quercusilex subsp. ballota) and mastic shrub (Pistacia lentiscus) seedlings to high concentrations of Cd and Tl in the rhizosphere. These are non-essential trace elements, with a potential high mobility in the soil-plant system. Seedlings of these species are frequently used in the afforestation of degraded soils in mining areas. Plants were exposed to different levels of Cd (20, 80 and 200 mg L⁻¹) and Tl (2, 10 and 20 mg L⁻¹) in a sand culture. Biomass allocation, growth rates, chlorophyll fluorescence and gas exchange were studied. Both metals affected root biomass. Cadmium produced an increase in the root mass ratio and a decrease in the specific leaf area of the plants in oak seedlings, while Tl did not provoke such response. Mastic plants were more sensitive to Tl and Cd than oak plants. Between elements, Tl provoked more severe toxic effects in the plants, affecting the antennae complexes and reaction centers of the photosystem II. Both elements decreased net assimilation rates (down to a 20% of the control plants) and stomatal conductance (5-10% of the values for the control plants). Cadmium was highly retained in the roots of both species, while Tl was highly translocated into the leaves. In general, Holm oak showed a higher tolerance for Cd than for Tl, and a higher resistance to both metals than mastic shrub, due to a high capacity for Cd retention at the root level. However, such accumulation in roots may induce water stress in the seedling exposed to Cd.     

Pasture composition in a trace element-contaminated area: the particular case of Fe and Cd for grazing horses

Pasture selection by livestock is an essential topic for rangeland management, especially in trace element-contaminated soils. We have studied the composition (nutrients and trace elements) of a grass-based diet from soils affected by a mine spill at different growth stages (October 2008 to May 2009). A diet based on other plants (mainly Compositae species) was also studied (May 2009) for comparison. Faeces and mane hair of horses feeding on these pastures were also analysed. Micronutrient (Cu, Fe, Mn and Zn) and potentially toxic trace element (As, Cd, Pb, Tl) concentrations were below the maximum tolerable levels (MTL) for horses, except for Fe (at early growth of pastures) and Cd (in the diet based on ‘other’ plants). Values of potential ingestion of Fe by horses were higher than 10 mg kg body weight^− 1 day^− 1. Cadmium concentrations in some pasture samples (those composed of Compositae species) were higher than 3 mg kg^− 1. Potential toxicity of such Cd levels in pastures is uncertain, since a high disparity of criteria about MTL by cattle exists (between 0.5 and 10 mg kg^− 1 diet). Nutrient concentrations were adequate for horses, which could counteract possible harmful effects derived from trace element ingestion. The analyses of excreta and mane hair point to the low risk of toxicity derived from the consumption of these contaminated pastures. However, the ingestion of regenerating pastures (autumnal samples) should be avoided due to the greater risk of ingestion of contaminated soil attached to the plant material. Management of these pastures by grazing requires periodic monitoring. Special attention should be given to Fe and particularly Cd (non-essential element) which accumulates in animal organs, where it could provoke uncertain long-term effects.     

Bioavailability and accumulation of trace elements in soils and plants of a highly contaminated estuary (Domingo Rubio tidal channel,SW Spain)

The Domingo Rubio tidal channel (Palos de la Frontera, Huelva, Spain) is an estuary located in the mouth of the Tinto River. The estuary is affected by different sources of pollution (waters of the Tinto River, contaminated with trace elements from the Iberian Pyrite belt, and effluent from the Huelva chemical industrial area). Soil and the most frequent plant species were collected in 2004 and 2006 at six different locations on the estuary. In general, N-Kjedahl, Total Organic Carbon values, salinity and contamination (total trace elements up to 1,000 mg kg⁻¹ As, 6 mg kg⁻¹ Cd, 2,500 mg kg⁻¹ Cu, 1,900 mg kg⁻¹ Pb and 1,300 mg kg⁻¹ Zn) tended to increase downstream of the tidal channel. Soil biochemical properties were not negatively affected either by the high salinity or by trace element contamination. Despite the high values of the trace elements, analysed plant samples showed that Cu was the only metal that could be a serious risk for the food chain.     

Accumulation of As, Cd and selected trace elements in tubers of Scirpus maritimus L. from Doñana marshes (South Spain)

The collapse of a pyrite-mining, tailing dam on 1998 contaminated an area of 4286 ha along the Agrio and Guadiamar river valleys in southern Spain. Over 2700 ha of the Do?ana marshes, an important wintering area for wetland European birds, were contaminated. This study reports analyses of the tubers of Scirpus maritimus (an important food for greylag geese, Anser anser) collected in 2000 in the "Entremuros" (spill-affected area) and in nearby unaffected Do?ana marshes (control areas). In the spill-affected area mean tuber tissue concentrations of Cd (0.25 mg kg-1) and Zn (61 mg kg-1) were greater than in those tubers from the control area (0.02 mg kg-1 for Cd, and 22 mg kg-1 for Zn); values of Cd and Zn in "Entremuros" (samples collected two years after the mine spill) were much smaller than those reported only a few months after the accident. Trace elements (As, Fe, Mn and Tl, and to a lesser extent Cd and Pb) showed a preferential accumulation in the outer skin of tubers. Surprisingly, concentrations of As and Fe were greater in tubers from some marsh sites not affected by the mine-spill than in tubers from the "Entremuros". We suggest that relic river channels within the Do?ana marshes may be contaminated by trace elements from historic mining activities. An exhaustive study of macrophytes and other plant species in this area is recommended to identify potential risks to wildlife.     

Trace element accumulation in woody plants of the Guadiamar Valley, SW Spain: a large-scale phytomanagement case study

Phytomanagement employs vegetation and soil amendments to reduce the environmental risk posed by contaminated sites. We investigated the distribution of trace elements in soils and woody plants from a large phytomanaged site, the Guadiamar Valley (SW Spain), 7 years after a mine spill, which contaminated the area in 1998. At spill-affected sites, topsoils (0-25 cm) had elevated concentrations of As (129 mg kg(-1)), Bi (1.64 mg kg(-1)), Cd (1.44 mg kg(-1)), Cu (115 mg kg(-1)), Pb (210 mg kg(-1)), Sb (13.8 mg kg(-1)), Tl (1.17 mg kg(-1)) and Zn (457 mg kg(-1)). Trace element concentrations in the studied species were, on average, within the normal ranges for higher plants. An exception was white poplar (Populus alba), which accumulated Cd and Zn in leaves up to 3 and 410 mg kg(-1) respectively. We discuss the results with regard to the phytomanagement of trace element contaminated sites.     

Optimisation of scrap automotive tyres recycling into valuable liquid fuels

The recycling of rubber from old tyres by batch hydrogenation has been performed using tubing bomb reactors. Important process variables like temperature, reaction time, initial hydrogen pressure and nature of gas used have been studied. In all the runs the maximum total conversion was achieved. Conversion products are comprised of oils and gases, being the asphaltene yield lower than 1% in all conditions tested. The most valuable conversion products, oils, have been systematically analysed by TLC-FID¹ and the influence of the process variables in oils composition has been assessed. From the obtained results, it can be deduced that the conversion of rubber in oils is a fast thermal process, which is neither affected by initial pressure nor the nature of gas used. But on the other hand, the nature of obtained oils and gases is a function of process variables.