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Highlights: [•] Two copper mine soils were reclaimed by planting trees and amending with wastes. [•] Both treatments significantly increased the total organic carbon content in mine soils. [•] Only the amendment increased the humified organic C to values of undisturbed sites. [•] It is recommendable the regular application of wastes to soils poor in organic matter. [ABSTRACT FROM AUTHOR]

Abstract: Mine soils are often physically degraded, which hinders plants development. The untreated soils at the depleted copper mine in Touro (Galicia, north-west Spain) have no vegetation and are probably physically degraded. These mine soils were reclaimed both by planting trees and amending with waste (sewage sludge and paper mill residues). The purpose was to determine the effect of these treatments on the physical quality of the soils of the Touro mine under field conditions. We evaluated the physical situation of both the settling pond and the mine tailings in Touro, then comparing them with their respective treated areas: vegetated, amended or with both treatments at the same time. We corroborated that the physical degradation of untreated soils was considerable: low porosity, high density and less than 50% of water stable aggregates. The trees that were planted increased porosity, probably due to root activity. The added amendments increased the mean weight diameter (MWD), the percentage of water stable aggregates (WSA) and the stability index (SI) due to the high organic carbon content in the added wastes. We verified that using both treatments at the same time is better than using only one to improve the physical situation of mine soils. [Copyright &y& Elsevier]

Abstract: Relatively new techniques can help in determining the occurrence of mineral species and the distribution of contaminants on soil surfaces such as natural minerals and organic matter. The Bt horizon from an Endoleptic Luvisol was chosen because of its well-known sorption capability. The samples were contaminated with Cu2+ and/or Pb2+ and both sorption and desorption experiments were performed. The preferential distribution of the contaminant species (63Cu and 208Pb) to the main soil components and their associations were studied together with the effectiveness of the surface sorption and desorption processes. The results obtained were compared with non-contaminated samples as well as with previous results obtained by different analytical techniques and advanced statistical analysis. Pb2+ competes favorably for the sorption sites in this soil, mainly in oxides and the clay fraction. Cu2+ and Pb2+ were mainly associated with hematite, gibbsite, vermiculite and chlorite. This study will serve as a basis for further scientific research on the soil retention of heavy metals. New techniques such as spectroscopic imaging and transmission electron microscopy make it possible to check which soil components retain heavy metals, thereby contributing to propose effective measures for the remediation of contaminated soil. [Copyright &y& Elsevier]

Abstract: It has often been stated that the contribution of soil organic matter (OM) to the sorption of heavy metals can be evaluated using the surface horizon of a Histosol as typical of soil organic matter. However, components of Histosols other than organic matter, such as clay minerals and Fe or Mn oxides, can also sorb heavy metals. In this work we compared the heavy metal sorption and desorption behaviour of a Fibric Histosol H horizon with that of its organo-mineral fraction (OMF, defined as the fraction of wet particle size <100μm) in experiments in which Cd, Cr, Cu, Ni, Pb and Zn were sorbed simultaneously from solutions of various concentrations. The OMF sorbed the metals reversibly and apparently mainly at specific sites to each particular metal, in keeping with the good fit of Langmuir isotherms to the sorption data; greatest sorption capacity was for lead and copper. Whole H horizon appeared to include sites at which binding was less reversible and chromium competed with the other metals, especially copper. Organo-mineral fraction is suggested to evaluate the soil organic matter contribution to heavy metal fixation. [Copyright &y& Elsevier]

The sorption and desorption of six heavy metals by and from the surface or immediately subsurface horizons of eleven acid soils of Galicia (N.W. Spain) were characterized by means of batch experiments in which the initial sorption solution contained identical mass concentrations of each metal. Concentration-dependent coefficients K d were calculated for the distribution of the metals between the soil and solution phases, and the values obtained for initial sorption solution concentrations of 100mgL−1 of each metal (K d100) were used, for each soil, to order the metals as regards their sorption and retention. Pb and Cu were sorbed and retained to a greater extent than Cd, Ni or Zn, which had low K d100 values. Pb was sorbed more than any other metal. Cr was generally sorbed only slightly more than Cd, Ni or Zn, but was strongly retained, with K d100 (retention) values greater than those of Pb and Cu in soils with very low CEC (<3cmol(+) kg−1). The sorption of Pb and Cu correlated with organic matter content, while the retention of these and the other metals considered appeared to depend on clay minerals, especially kaolinite, gibbsite, and vermiculite. [Copyright &y& Elsevier]

In Part I of this paper we reported, for each of 11 acid soils, the rankings of six metals according to their sorption from solutions containing all six, and according to their retention under desorption conditions. Here, we analyse the same data from a different perspective: for each metal, we rank the soils by their capacities to sorb and retain it as reflected by soil/solution distribution coefficients K d100 measured using starting solutions containing 100mgL−1 of each metal. We also ranked the soils for overall heavy metal sorption and retention capacities using Kaplan's compound measure K dΣ, and we investigated the influence of soil characteristics on K d100 and K dΣ100 values. Overall capacity for sorption of heavy metals was positively related to HOM, kaolinite and Fe oxides contents, and negatively related to CEC and to vermiculite and haematite contents. Overall capacity for retention of heavy metals was positively related to HOM and kaolinite contents, and negatively related to CEC and vermiculite content. The good correlation between K dΣ100(sorption) and the first component extracted in a principal components analysis of K d100(sorption) values, and between K dΣ100(retention) and the first component extracted in a principal components analysis of K d100(retention) values, supports the adequacy of K dΣ as a measure of the overall capacity of a soil to sorb or retain heavy metals. [Copyright &y& Elsevier]

Shooting activities is an important source of Pb in contaminated soils. Lead accumulates in superficial soil horizons because of its low mobility, favouring its uptake by plants and representing a high transference risk to the trophic chain. A combination of phytoremediation with nanoremediation techniques can be used to recover firing range soils and decrease the mobility, bioavailability and toxicity of Pb. This study examines in depth the changes in Pb behaviour in firing range soils by adding hydroxyapatite nanoparticles (HANPs). These nanoparticles (NPs) may immobilise Pb and improve the quality of these areas. The use of HANPs and the Pb effects were assessed in three different species (Sinapis alba L., Lactuca sativa L. and Festuca ovina L.), focusing on their germination and early growth, through phytotoxicity assays. Single extractions with CaCl 2 (0.01 M) in soils treated with HANPs show that these NPs retained Pb and reduced highly its availability and mobility. HR-TEM and TOF-SIMS were used to determine the interactions between HANPs and Pb, as well as with soil components. According to TOF-SIMS and HR-TEM/EDS analysis, Pb was mainly retained by HANPs but also associated lightly to organic matter, Fe compounds and silicates. Phytotoxicity assays exposed that S. alba , L. sativa and F. ovina were able to germinate and develop in the firing range soils despite the high available Pb contents before adding HANPs. After adding HANPs, Pb retention increased, favouring the germination and the growth of roots in the three species. These results suggest that HANPs can be used to decrease the availability and the toxicity of Pb without negative effects in the species growth. Accordingly, the combination of phytoremediation and nanoremediation techniques can be a great tool to stabilise these soils, avoiding the Pb transfer to nearby areas and its entry in the trophic chain. Unlabelled Image • HANPs reduce efficiently the available Pb contents in firing range soils. • HANPs favour the germination and root growth of S. alba , L. sativa and F. ovina. • TOF-SIMS/HR-TEM allow to assess the interactions among HANPs, Pb and soil components. • Pb mobility, availability and toxicity decrease greatly after treatment with HANPs. • Nanoremediation and phytoremediation can be effective to recover firing range soils. [ABSTRACT FROM AUTHOR]

Abstract São Domingos mine is one of the most important abandoned mines in the Iberian Pyrite Belt (IPB) (SE, Portugal), which has large amounts of waste deposited in tailings. Weathering causes sulphide oxidation, acid mine drainage, leaching of high levels of potentially hazardous elements (PHEs) and, consequently, environmental degradation in surrounding areas. The use of nanoparticles (NPs) to recover contaminated soils from IPB can be an effective tool compared to the use of traditional amendments, due to small size, high specific surface and reactivity of NPs. The combination of nanoremediation techniques, together with the current phytoremediation techniques carried out in the IPB, could improve the immobilisation and decrease the availability of PHEs in these soils. In this research was assessed whether the use of hydroxyapatite (HANPs), hematite (HMNPs) and maghemite (MNPs) nanoparticles are effective for recovery degraded soils. Extractable contents of As, Pb and Sb were determined in soils treated (with NPs) and non-treated. Three different extractants based on CaCl 2 (0.01 M), low molecular weight organic acids (LMWOA - 10 mM) and ultrapure water (UPW) were used. Extractable contents of Pb, As and Sb in the soil samples treated with NPs decreased; and HANPs were those that most bioavailable Pb retained. In addition, the NPs were characterised in shape, size and elemental composition before and after being applied to the soil samples using High Resolution Transmission Electron Microscopy with Energy Dispersive X-ray Spectroscopy (HR-TEM/EDS). After treatment, the NPs associated to As, Pb and Sb were identified in the mine soils. The great decrease of PHEs bioavailability was possible due to the association of PHEs with the NPs, which reduce considerably the mobility of PHEs in mine soils. Graphical abstract Unlabelled Image Highlights • Phosphate and iron oxide NPs were efficiency to reduce PHEs contents in mine soils. • Available and soluble Pb decreased mainly in mine soils treated with HANPs. • The fixation of As was much more efficient with HMNPs or MPS than with HANPs. • HR-TEM/EDS allow visualising the association of PHEs with the NPs added to the soils. • Nanoremediation is an efficient technique to recover soils with high PHEs contents. [ABSTRACT FROM AUTHOR]

Soil pollution at firing ranges is an issue of growing importance, due to the accumulation in soils of contaminants derived from ammunition and clay targets. The concentration of Pb and PAHs was determined in five soils of an abandoned shooting range in Galicia (northwest Spain), and an ecotoxicological characterization was performed in order to obtain an assessment of risks. Therefore, the retention capacity of soils was assessed using test organisms of different trophic levels, and the role of soils as habitat for soil invertebrates was assessed by reproduction tests and bioaccumulation assays with earthworms. The sum of 15 PAHs ranged between 38 and 360 mg kg − 1 , which exceed, together with Pb (160–720 mg kg − 1 ), the Galician generic reference value for urban and sporting field soils. Bioaccumulation in E. andrei showed contents up to 104,000 μg Pb kg − 1 dw , and up to 645 μg PAHs kg − 1 fw . High contents of Pb and PAHs in soil samples and in Eisenia andrei whole body, caused a reduction in the number of juveniles produced, whereas, Vibrio fischeri , Raphidocelis subcapitata and Daphnia magna displayed a slight toxic response to the soil elutriates tested. Therefore, the function of these soils to retain contaminants seemed not compromised, probably due to the high organic matter content and pH values, which are weakly acidic. The habitat function was affected, indicating that soil solution is not the only route of exposure to contaminants to E. andrei . The integration of chemical and ecotoxicological lines of evidence give rise to high risks values, restricting the use of these areas, and pointing for risks to surrounding ecosystems due to possible trophic transferences. The calculation of risks using the chemical and ecotoxicological data, required by Spanish legislation, could be a good approach to communicate with those responsible and/or involved in the management of contaminated sites. [ABSTRACT FROM AUTHOR]

Shooting activities are a very important source of contamination as they are commonly detected high concentrations of Pb in the soils from these facilities. Different remediation methods imply the immobilization of the pollutants by decreasing their mobility and availability and nanotechnology is a promising technique in this field. The effectiveness of calcium phosphate nanoparticles (CPNs) in the remediation of small-arms firing range and trap shooting range soils is evaluated in this work. The operationally defined extractable content of Pb, Cu and Zn is determined together with the interaction of the pollutants with the nanomaterials. Soil samples were treated with the CPNs and after the treatment the extractable contents of Cu, Pb and Zn decrease. To check the retention by the nanoparticles TOF-SIMS (Time of Flight Secondary Ion Mass Spectrometry) and HR-TEM-EDS (High Resolution Transmission Electron Microscopy with Energy Dispersive X-ray Spectroscopy) techniques were applied. The association of Pb and Cu to the CPNs was demonstrated by TOF-SIMS although it also indicated that not all the Pb and Cu contents are linked to the nanoparticles. By means of HR-TEM/EDS it was made out the filamentous shape and the size (50–150 nm long and 20–40 nm wide) of the CPNs together with their elemental composition (Ca, P and O). The CPNs were identified in treated soil samples together with signals of metals. The decrease on metal extractability detected is, in part, due to the association with CPNs but still more investigation is needed regarding mobility and availability of potentially hazardous elements in soils treated with nanoparticles. [ABSTRACT FROM AUTHOR]