Journal of Hazardous Materials 268 (2014) 68–76

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Evaluation of the phytostabilisation efficiency in a trace elements contaminated soil using soil health indicators T. Pardo a,∗ , R. Clemente a , L. Epelde b , C. Garbisu b , M.P. Bernal a a Department of Soil and Water Conservation and Organic Waste Management, CEBAS-CSIC, Campus Universitario de Espinardo, P.O. Box 165, 30100 Murcia, Spain b Department of Ecology and Natural Resources, Soil Microbial Ecology Group, NEIKER-TECNALIA, Berreaga 1, 48160 Derio, Spain

h i g h l i g h t s • • • • •

Microbial and ecotoxicological parameters were evaluated in a phytostabilised soil. Amendments enhanced soil habitat function, nutrients cycles and reduced toxicity. Nutrients stimulated the growth, activity and diversity of soil microorganisms. Soil health increased after addition of amendments and A. halimus establishment. Using compost with A. halimus is suitable for semi-arid mine soils remediation.

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Article history: Received 21 October 2013 Received in revised form 18 December 2013 Accepted 3 January 2014 Available online 8 January 2014 Keywords: Heavy metals Arsenic Organic amendments Ecotoxicological bioassays Soil functional diversity

a b s t r a c t The efficiency of a remediation strategy was evaluated in a mine soil highly contaminated with trace elements (TEs) by microbiological, ecotoxicological and physicochemical parameters of the soil and soil solution (extracted in situ), as a novel and integrative methodology for assessing recovery of soil health. A 2.5-year field phytostabilisation experiment was carried out using olive mill-waste compost, pig slurry and hydrated lime as amendments, and a native halophytic shrub (Atriplex halimus L.). Comparing with non-treated soil, the addition of the amendments increased soil pH and reduced TEs availability, favoured the development of a sustainable vegetation cover (especially the organic materials), stimulated soil microorganisms (increasing microbial biomass, activity and functional diversity, and reducing stress) and reduced direct and indirect soil toxicity (i.e., its potential associated risks). Therefore, under semi-arid conditions, the use of compost and pig slurry with A. halimus is an effective phytostabilisation strategy to improve soil health of nutrient-poor soils with high TEs concentrations, by improving the habitat function of the soil ecosystem, the reactivation of the biogeochemical cycles of essential nutrients, and the reduction of TEs dissemination and their environmental impact. © 2014 Elsevier B.V. All rights reserved.

1. Introduction Soil contamination by trace elements (TEs) due to mining activities generally involves the modification of its ability to sustainably develop its potential ecological functions and may affect adjacent ecosystems, i.e. alter soil functioning and health [1,2]. This is the case of the mining area of the Sierra Minera of La Unión-Cartagena (Murcia, SE Spain), where the intense mining activity carried out for over 2500 years has given rise to highly contaminated soils with unfavourable conditions for plant growth (high levels of TEs, low organic matter and nutrient contents, high salinity, poor physical structure, etc.), most of them unable to support a vegetation cover to protect the soils from wind and water erosion [3,4]. To

∗ Corresponding author. Tel.: +34 968396264; fax: +34 968396213. E-mail addresses: [email protected], [email protected] (T. Pardo). 0304-3894/$ – see front matter © 2014 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.jhazmat.2014.01.003

face this problem, phytostabilisation, based on the use of native tolerant plants and agricultural practices, could be a valuable and cost-effective option to remediate this type of soils [4], reducing in situ the toxicity and dissemination of TEs while promoting soil natural processes [5]. The assessment of the recovery of soil health after a remediation procedure will allow the evaluation of its effectiveness and, thus, to optimise its application in future restoration processes [2,6]. The use of indicators related to soil physicochemical, ecological and ecotoxicological characteristics, which combine laboratory tests and field monitoring, seems to be a suitable screening methodology of soil health [7,8], allowing the evaluation, not only of soil functioning, but also of its associated risks. Parameters related to the soil microbial ecology, especially those dealing with the size, activity and diversity of soil microbial communities, are considered as potentially sensitive, early and effective indicators of soil health [9,10], and have been proposed as useful

T. Pardo et al. / Journal of Hazardous Materials 268 (2014) 68–76

tools to evaluate and assess the effectiveness of the remediation of TEs contaminated soils [11–13]. For example, increases in soil biomass-C and N [4], hydrolase activities related with the major nutrient cycles [1,14,15], mineralisation of N [6], microbial respiration [2] or diversity indexes [6,16,17] have been reported in different TEs contaminated soils after a remediation process, reflecting the amelioration of soil functioning. Nevertheless, just a few studies in highly TEs contaminated mine spoil soils that integrate these indicators with ecotoxicological parameters can be found in the literature (e.g. [18–20]). Ecotoxicological assays (direct and indirect tests) can reflect soil toxicity by showing the effects of the interactions between the contaminants, the soil matrix and the living organisms in it [21,22]. In TEs contaminated soils, ecotoxicological tests have generally been applied alone or in combination with chemical analyses to evaluate the soil’ potential ecological risks [22,23], but this approach does not provide a global view of the remediation process effect on soil health. The aim of this work was to evaluate the efficiency of the application of organic wastes and lime as soil amendments, in combination with a native plant species, on the phytostabilisation of a mine TEs contaminated soil from the Sierra Minera of La Unión-Cartagena by studying the recovery of soil health. The short-term effects of these treatments on chemical properties of TEs contaminated soils and their evolution under field conditions have been reported in previous studies [4,13], but their effectiveness to recover soil health is evaluated at the field conditions in the present paper. After 2.5 years of field experimentation, the success of the phytostabilisation process on soil health recovery was evaluated through the study of the physicochemical properties of the soil and soil solution (extracted in situ), soil microbial parameters, and direct and indirect ecotoxicological bioassays. 2. Materials and methods 2.1. Experimental set-up A field phytostabilisation experiment was located in a mine spoil soil contaminated with trace elements (Table 1) near the village of El Llano del Beal (Murcia, SE Spain). Two organic materials and an inorganic liming substance were used as soil amendments: mature olive mill-waste compost (60 t ha−1 ), fresh pig slurry (60 m3 ha−1 ) and hydrated lime (2.3 t ha−1 ). Four replicates per treatment were randomly distributed in 12 plots of 2 m2 (2 m × 1 m) leaving 0.5 m aisles between plots. In each plot, one sub-plot of 1 m2 was planted with the native halophytic shrub Atriplex halimus L., and another

Table 1 Characteristics of the soil and the organic amendments. Characteristics

Soil

Compost

Pig slurrya

pH EC (dS m−1 ) CEC (cmolc kg−1 ) OM (%) TOC (g kg−1 ) Total-N (g kg−1 ) Total-P (g kg−1 ) Available-P (g kg−1 ) Available-As (mg kg−1 ) As (mg kg−1 ) Cd (mg kg−1 ) Cu (mg kg−1 ) Fe (g kg−1 ) Mn (mg kg−1 ) Pb (mg kg−1 ) Zn (mg kg−1 )

6.2 ± 0.1 2.7 ± 0.01 6.9 ± 0.3 0.2 ± 0.01 1.3 ± 0.1 0.4 ± 0.05 na 0.07 ± 0.04 0.39 ± 0.01 664 ± 28 19 ± 1 193 ± 8 108 ± 1.1 4073 ± 368 10,188 ± 97 9686 ± 251

8.8 ± 0.01 6.1 ± 0.2 na 73.1 ± 0.3 438.6 ± 7.9 31.7 ± 0.8 4.9 ± 0.1

Evaluation of the phytostabilisation efficiency in a trace elements contaminated soil using soil health indicators.

The efficiency of a remediation strategy was evaluated in a mine soil highly contaminated with trace elements (TEs) by microbiological, ecotoxicologic...
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