Evaluation of tests to assess the quality of mine-contaminated soils

Abstract

An acid metal-contaminated soil from the Aljustrel mining area (a pyrite mine located in SW Portugal in the Iberian Pyrite Belt) was subjected to chemical characterisation and total metal quantification (Cd, Cr, Cu, Ni, Pb and Zn). Water-soluble metals were determined and a sequential extraction procedure was used to investigate metal speciation. Two bioavailable metal fractions were determined: a mobile fraction and a mobilisable fraction. Soil ecotoxicity was studied using a battery of bioassays: plant growth test and seed germination with cress (Lepidium sativum L.), earthworm (Eisenia fetida) mortality, E. fetida avoidance behaviour, luminescent inhibition of Vibrio fischeri and Daphnia magna immobilisation. Although the total content of Cu, Zn and Pb in the soil was large (362, 245 and 1,250 mg/kg dry matter, respectively), these metals were mostly structurally bound (87% for Cu, 81% for Zn and 89% for Pb) and, therefore, scarcely bioavailable. Nonetheless, the D. magna immobilization test using soil leachate showed an EC50 (48 h) of 36.3% (v/v), and the luminescent inhibition of V. fischeri presented an EC20 (15 min) of 45.2% and an EC20 (30 min) of 10.7% (v/v), suggesting a considerable toxic effect. In the direct exposure bioassays, E. fetida avoided the mine soil at the highest concentrations (50%, 75% and 100% v/v). At the same soil concentrations, cress showed negligible growth. The results suggest the need to use a battery of toxicity tests, in conjunction with chemical methods, in order to assess the quality of mine-contaminated soils correctly.

Application of an inverse neural network model for the identification of optimal amendment to reduce copper toxicity in phytoremediated contaminated soils

“…For example, the proposed inverse ANN model generated solutions composed of mixed amendments as the optimal treatment (Fig. 3) which is in agreement with previous studies where the authors applied individual combinations of different amendments (Alvarenga et al,2008;Farrell and Jones, 2010;Warren and Alloway, 2003;Gadepalle et al, 2008;Bes and Mench, 2008). The present study showed that a plausible innovative low-cost strategy for the optimal remediation of contaminated soils in situ could be performed using such inverse ANN approaches.…”

“…In previous studies, numerous amendments have been incorporated into soils polluted with metal (metalloids) to immobilize pollutants. These amendments include individual additions of amendments (Walker et al, 2004;Schwab et al, 2007;Derome, 2009;González-Alcaraz et al, 2011;Melamed et al, 2003;Brown et al, 2005;Ford, 2002;Trivedi and Axe, 2001;Hartley and Lepp, 2008;Gupta and Sharma., 2002;Garau et al, 2011;Brown et al, 2003;Torri and Lavado, 2008) and combinations of different amendments including organic and liming materials (Alvarenga et al,2008;Farrell and Jones, 2010;Bes and Mench, 2008), iron oxides and lime (Warren and Alloway, 2003) and compost and iron oxide (Gadepalle et al, 2008).…”

Geochemistry and environmental threats of soils surrounding an abandoned mercury mine

“…The observed toxic effects in the bacterial bioluminescence inhibition assay were not sufficient to estimate EC50 values for samples A1, A3, A5 and A7 whereas extracts A2 and A4 were very toxic and A6 presented moderate toxicity. The lesser sensitivity of V. fischeri luminescence towards leachates from mine soils was previously documented (Alvarenga et al 2008;Maisto et al 2011) and might be related with the pH correction of the leachate suggested by standard methods (Alvarenga et al 2013). In contrast, the growth inhibition of the microalgae R. subcapitata showed an extreme sensitivity that correlated significantly with Zn content in water extracts (r = 0.996, p < 0.01).…”

“…More recently, it was concluded that chemical extractions of metals from multi-contaminated soils did not provide enough information about their bioavailable fractions (Alexander 2000;Ehlers and Luthy 2003;Semple et al 2004;Harmsen 2007) and were not able to reflect the toxicity of all substances in soil, their synergic and antagonistic effects and their interactions with the soil matrix and organisms (Gruiz 2005). In this context, th e application of batteries of terrestrial ecotoxicity tests gained special relevance as complementary, inexpensive, simple and quick tools able to report realistic and nonoverestimated effects of contaminated sites to soil organisms (Leitgib et al 2007;Alvarenga et al 2008;Maisto et al 2011;Alvarenga et al 2012;Agnieszka et al 2014;Bes et al 2014;. At the same time, aquatic bioassays traditionally applied for the toxicity determination of aquatic pollutants (Lopez-Roldan et al 2012), industrial effluents (Riva et al 1993;Riva and Valles 1994;Riva et al 2007) or extracts of sediments (Pereira-Miranda et al 2011) were incorporated to assess the impacts of soil composition and runoffs on receiving waters (Loureiro et al 2005a;Rocha et al 2011).…”

Amendment application in a multi-contaminated mine soil: effects on soil enzymatic activities and ecotoxicological characteristics

“…The resilience of this organism to adverse conditions is well known, compromising the use of the acute toxicity test with E. fetida to detect low toxicity values (Alvarenga et al 2008b(Alvarenga et al , 2012. Taking these results into account, the avoidance behaviour tests in 'Fe' amended soils were carried out only with the 12.5; 25; and 50% (w/w) soil test dilutions with artificial soil, while the rest of the treatments, which did not induce earthworm mortality after 14 days of exposure, were tested using the complete set of dilutions, 12.5; 25; 50 and 100% (w/w) ( Table 5).…”