An integrated geochemical and mineralogical investigation on soil-plant system of Pinus halepensis pioneer tree growing on heavy metal polluted mine tailing

Abstract

The plant species Pinus halepensis grows spontaneously on heavily polluted mine tailings dumps of Campo Pisano (Sardinia, southwestern Italy). The area is characterized mainly by Zn, Pb, and Cd.Sampling campaign was done, related to soils and plant materials (roots, barks, wood, and needles), aimed at evaluating the main mineralogical characteristics, metal content, plant accumulation, and translocation behavior. The polluted substrates were composed of pyrite, dolomite, calcite, quartz, gypsum, and barite with iron sulphate, and iron oxide. Zn ore minerals (smithsonite) and muscovite detected mostly in the deeper soil layers. Zn was the most abundant metal in the substrate as well as plant tissues. Roots accumulated high metal concentrations (664.65-2710 Zn, 58.39-735.88 Pb, and 4.86-11.02 mg kg -1 Cd) reflecting high metal contamination in soil. The biological accumulation and translocation values were reported below one for all plant tissues. Pb, Zn and Cd Translocation Factor (TF) in needles ranged 0.03-0.32, 0.03-0.19, 0.04-0.14. Biological Concentration Factor (BCF) estimated up to 0.17, 0.18, and 0.19, respectively. A c c e p t e d M a n u s c r i p t 2Results indicate that P. halepensis is an excluder, tolerates high Zn, Pb, and Cd concentrations, restricts their accumulation and translocation to the aerial parts and may be applied for long-term phytostabilization and revegetation processes in abandoned mine tailing sites.

Pinus halepensis in Contaminated Mining Sites: Study of the Transfer of Metals in the Plant–Soil System Using the BCR Procedure

“…Six Pinus halepensis specimens with a nearly similar height (2 m) and age (10-12 years old) were selected from both non-contaminated and contaminated sites in the south-west of Sardinia (November 2020) where they grow spontaneously (Figure 1a,b). Six bulk soil samples were collected from the soils around the roots of P. halepensis together with its root samples: (i) CP1: located inside the contaminated Campo Pisano (CP) site in the compost-amended plot aged 10 years old [10,37], (ii) CP2: outside of the CP experimental plot distancing 3-4 m from it aged 10 years old, and (iii) CP3: located outside of the CP experimental plot distanced 6-7 m from it and aged 12 years old (Figure 1c,d) (see more in [32]), (iv) B1: Blank sample in the non-contaminated site (Santa Margherita, Pula) at approximately 80 km far away from CP mine site, (v) B2: Blank sample in the noncontaminated site (Calamosca, Cagliari) at about 60 km far away from the CP mine site, (vi) B3: Blank sample from the less-contaminated site (Fontanamare, Gonnesa) at about 10 km distance from the CP mine site (Figure 1b). The contaminated soils around the root and root samples were exploited the previous study [32].…”

“…Three soil in-depth core-drilled samples (approximately 70 cm) were also collected from the CP-contaminated mine sites using a core sampler (Atlas Copco's COBRA): (i) the first sample in the experimental plot at approximately 50 cm distance from the tree (S1), (ii) the second one in a bare site, out of the experimental plot, where there is no vegetation canopy (S2), (iii) the third sample in the amended plot at 1-2 m distance from the pine (S3) (Figure 1d); see more in [32]. The three soil samples were selected from each coredrilled sample, according to the visually recognizable color of the soil substrate and their mineralogical and geochemical characteristics that were investigated in our previous research study [32]. These layers were selected for BCR analysis, regardless of their soil depth horizon, to provide a better interpretation of their metal availability.…”

“…A preliminary study was carried out in the abandoned mine tailing site of Campo Pisano (SW-Sardinia) by our research group in 2020 to investigate the contaminated soils and different compartments (roots, barks, wood and needles) of Pinus halepensis and to evaluate the metal content, plant accumulation and translocation behavior as well as the main mineralogical characteristics of Zn, Pb and Cd [32]. The findings showed that despite the detection of a high concentration of metals in the soil, the estimated Biological Accumulation Coefficient and Translocation Factor (BAC, BCF and TF < 1) were very low.…”

“…These findings indicated that P. halepensis has a qualified metal toleration capability and has limited metal accumulation and translocation factors in the aerial parts. Thus, this plant can be considered as an excluder plant and a candidate for phytostabilization projects [32].…”

“…The aim of this study was to determine the geochemical fractions of Zn, Pb and Cd and the specific geochemical forms of elements present in the same sampling site through the three-step BCR extraction method in relation to the physico-chemical and mineralogical characteristics of the soil in depth and the soil-root system. In order to pursue this aim, the study exploited the pertinent data of mineralogical and chemical analysis of contaminated soil and root samples available in Kharazian et al (2022) [32].…”