Aluminum speciation in the bulk and rhizospheric soil solution of the species colonizing an abandoned copper mine in Galicia (NW Spain)

Abstract

Purpose The present study was carried out to identify and quantify the aluminum species present in the bulk and rhizospheric soil solution of the spontaneous vegetation colonizing the dump (Calluna vulgaris, Erica cinerea) and slope (C. vulgaris, E. cinerea, Salix atrocinerea) of an abandoned Cu mine in Touro (Galicia, NW Spain). Materials and methods Total dissolved aluminum was speciated into reactive Al (Alr) and acid-soluble Al (Alsa). Acid-soluble aluminum comprises colloids, polymers and/or organo-aluminum complexes, whereas Alr comprises nonlabile monomeric aluminum (AlnL) and labile monomeric aluminum (AlL). The latter fraction included Al 3+ , Al-OH complexes, Al-F complexes, and Al-SO 4 complexes. Results and discussionThe results show that Ericaceae modified the pH of the rhizosphere from 6.6 to 4.0 (C. vulgaris) in the slope, whereas S. atrocinerea only grew in close-to-neutral soil conditions and increased the rhizosphere pH by 0.8 units. The total concentration of Al in the soil solution was low (<75 μmolL -1 ) and was higher in the rhizosphere than in the bulk soil solution in all samples. Under Ericaceae, the Alr represented between 80% and 98% of the total Al in solution and the concentration was higher in the rhizosphere; under S. atrocinerea the Alsa was always higher than 80%, with higher concentrations in the rhizosphere. AlL predominated over AlnL in all samples. The distribution of labile Al into different species depended on the pH and the concentration of labile Al: Al 3+ predominated in all samples from the dump (>40% of the AlL) and in the C. vulgaris rhizosphere in the slope (>52% of the AlL); the Al-F complexes were more abundant in the E. cinerea rhizosphere in the slope (>40% of the AlL), and Al-OH complexes predominated in all samples associated with S. atrocinerea (>70%). In the mine dump, the Ca/AlL ratio changed from 0.07 (bulk soil) to higher than 1.4 in the root zone of the Ericaceae thus decreasing the risk of toxicity by this element. Conclusions Labile aluminum is the prevailing fraction in all dump samples and in the rhizosphere of Ericaceae growing on the slope. Al 3+ is the predominant species in the most acidic samples with the highest concentration of labile Al and the highest AlL/F ratio. In areas where there may be a risk of Al toxicity, Ericaceae accumulated Ca in the vicinity of the roots, thus increasing the Ca/AlL ratio relative to that in the bulk soil and preventing absorption of Al and the associated phytotoxicity.

Dechlorinating transformation of propachlor through nucleophilic substitution by dithionite on the surface of alumina

“…Alumina surfaces have been found to be more reactive when compared with many other soil minerals, and this reactivity has been widely used for fabricating adsorbents (Al-Abadleh and Grassian 2003;Essington and Anderson 2007;Álvarez et al 2011;Wang and Shih 2011) and catalysts (Hass et al 1998;He et al 2005). Dried aluminas commonly chemisorb at least a monolayer of water when exposed to moisture at ambient conditions, and when the surfaces are hydrated, the top layer of oxide ions will be converted into a filled and square lattice of hydroxyl ions (Goldberg et al 1994).…”

How Do Plants and Climatic Conditions Control Soil Properties in Hypersaline Tidal Flats?

“…Each sampling site was georeferenced using a portable GPS and the coordinates of each site were used for the measurement of the distance to the nearby river using geoprocessing techniques. At the laboratory, the soil adhered to the roots were removed for analysis by gently shaking and brushing the soil-rhizosphere system [37][38][39][40]. Subsequently, the samples of bulk and rhizospheric soil were air-dried, crushed, and 2-mm sieved, whereas subsamples were frozen for posterior determination of iron forms by a sequential extraction procedure.…”

Copper release from waste rocks in an abandoned mine (NE, Brazil) and its impacts on ecosystem environmental quality

“…Despite the large number of studies that demonstrated the environmental problems caused by abandoned mines, just a few estimated the actual potential of waste rock piles to release metals to the surrounding ecosystems (Stromberg and Banwart, 1999;Jurjovec et al, 2002). These studies involved a detailed identification of the geochemical composition of the mine wastes, as well as their behaviour when in contact with water and soil ( Alvarez et al, 2010( Alvarez et al, , 2011Otero et al, 2012). These factors define the amount of metal that can be released by wastes and it also defines how the leachates behave in contact with natural resources, which may favour or hinder the metal bioavailability for living beings (Langman et al, 2014).…”