Uptake of potentially toxic elements by edible plants in experimental mining Technosols: preliminary assessment

Abstract

A study was carried out to evaluate the absorption of potentially toxic elements from mining Technosols by three types of vegetable plants (broccoli (Brassica oleracea var. italica), lettuce (Lactuca sativa) and onion (Allium cepa)), the different parts of which are intended for human and farm animal consumption (leaves, roots, edible parts). The preliminary results obtained highlight the importance of the design of the mining Technosols used for agricultural purposes, obtained from soils and sediments of mining origin and amended with residues of high calcium carbonate concentrations (limestone filler and construction and demolition wastes). The experiment was carried out in a greenhouse, and the total metal(loid)s concentration (As, Pb, Cd, Cu, Fe, Mn and Zn) of the soil, rhizosphere, aqueous leachates and plant samples was monitored, the translocation and bioconcentration factors (TF and BCF, respectively) being calculated. The characterization of the soils included a mobilization study in media simulating different environmental conditions that can affect these soils and predicting the differences in behavior of each Technosol. The results obtained showed that the levels of potentially toxic elements present in the cultivated species are within the range of values mentioned in the literature when they were cultivated in soils with calcareous amendments. However, when the plants were grown in contaminated soils, the potentially toxic elements levels varied greatly according to the species, being higher in onions than in lettuce. Experiments with the use of lime filler or construction and demolition wastes for soil remediation result in crops that, in principle, do not present health risks and are similar in development to those grown on non-contaminated soil.

Keywords: Arsenic; Metal(loid)s; Plant uptake; Soil remediation; Technosols.

Fig. 1

Location of the study area. Graphical summary of the way of preparation of the Technosols

Fig. 2

Results of the mobility study of PTEs in the Technosols (T1, T2, T3, T4 and TC) expressed in percentage of element extraction in the extractant medium referred to the total concentration of the element (W = water; A = acidic medium; MJ = complexing and reducing medium; O = oxidizing medium)

Fig. 3

Temporal evolution of parameters in the leachates obtained from Technosols (T1, T2, T3, T4 and TC) in the cultivation period

Fig. 4

Levels of PTEs (median ± standard deviation) in the edible plants studied

Fig. 5

Graphical plots obtained in principal components analysis (F1 versus F2). a) Lettuce (Lactuca sativa), b) broccoli (Brassica oleracea var. italica), c) onion (Allium cepa)

Fig. 6

Bioconcentration factor (BCF) and transfer factor (TF) values (median ± standard deviation) for the different plants and Technosols

Fig. 7

Diagram including the main physicochemical processes and conditions involved in the construction of a Technosol