Abstract
This study is focused on one of the most important spills that ever happened in Europe, the Aznalcóllar’s mine spill. The extensive application of phytostabilization in the area led to the implementation of the Guadiamar Green Corridor (GGC). Soil physicochemical properties were analyzed and the total concentration of Pb, As, Zn and Cu was measured by X-ray fluorescence (XRF); bioassay using Lactuca sativa L. was applied to assess potential toxicity. Two decades after the accident, some soils affected by residual contamination continue to appear in the area. According to regulatory levels, Pb and As concentrations are exceeded in around 13%and 70%, respectively, in the uppermost part of the soils (first 10 cm). The change in soil properties after bioremediation treatment positively promoted the reduction in the potential mobility of pollutants by the increase in pH, CaCO3 content and organic carbon. Anyway, the bioassay with Lactuca sativa, indicated that around 25% of the soils showed toxicity by the reduction of the root elongation in relation to the control samples. Our results indicate that monitoring of the GGC is still needed, together with the application of soil recovery measures to reduce the potential toxicity in some sectors of the affected area.
Highlights
Soil contamination with potentially harmful elements (PHEs) is a growing concern and ubiquitous around the globe
Soils affected by the spill were related to the fluvial regime, involving the main soil groups usually found in this environment: Fluvisols and Regosols according to International Union of Soil Sciences (IUSS) Working Group World Reference Base for soil resources (WRB) [20] or Entisols according to SSS [21]
According to the main properties, the Guadiamar Green Corridor (GGC) was divided into two sectors: (1) Sector 1 (S1), involving soils with acidic pH (5–6), mean CaCO3 content
Summary
Soil contamination with potentially harmful elements (PHEs) is a growing concern and ubiquitous around the globe. According to He et al [1], more than 10 million contaminated sites exist worldwide related to anthropogenic sources and activities; for instance, 137,000 km of agricultural land in Europe needs local assessment and eventual remediation action in relation to the heavy metal concentrations [2]. Remediation actions to remove these PHEs from the soil are usually expensive, time-consuming or need the application of ex-situ technologies that are not able to develop in large areas. In many cases the remediation is focused in the application of amendments to reduce the bioavailability and to promote the immobilization of pollutant into the soil matrix, followed by a stabilization of the soil surface by vegetation (phytostabilization) [5], implying that these areas increase the background concentrations
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